refactor(tasks): stabilize grouped board headers

frontend/src/app/globals.css

@@ -899,6 +899,19 @@ html[data-bs-theme="dark"] .shadow-xl {
   box-shadow: var(--shadow-card) !important;
 }
 
+html[data-bs-theme="dark"] .tasks-board-column-header,
+html[data-bs-theme="dark"] .tasks-board-subcolumn-header {
+  box-shadow: none !important;
+}
+
+html[data-bs-theme="dark"] .tasks-board-column-header-sticky {
+  background: var(--surface-elevated);
+}
+
+html[data-bs-theme="dark"] .tasks-board-group-header-sticky {
+  background: var(--surface-elevated);
+}
+
 
 /* Скрытые полосы прокрутки везде */
 * {
@@ -1001,35 +1014,66 @@ html[data-bs-theme="dark"] .shadow-xl {
     --tasks-board-stack-gap: 0.5rem;
     --tasks-board-column-header-height: 4rem;
     --tasks-board-subcolumn-header-height: 4rem;
+    --tasks-board-group-header-stack-height: calc(
+      var(--tasks-board-column-header-height, 4rem)
+      + var(--tasks-board-stack-gap, 0.5rem)
+      + var(--tasks-board-subcolumn-header-height, 4rem)
+      + 1rem
+      + 1px
+    );
   }
 
-  .tasks-board-column-header {
+  .tasks-board-column-header-sticky {
     position: sticky;
     top: 0;
     z-index: 30;
+    padding-bottom: var(--tasks-board-stack-gap, 0.5rem);
+    background: var(--background);
+  }
+
+  .tasks-board-column-header-sticky-standalone {
+    padding-bottom: 0;
+  }
+
+  .tasks-board-column-header {
     min-height: var(--tasks-board-column-header-height, 4rem);
     background: var(--surface-elevated);
   }
 
-  .tasks-board-subcolumn-header-row {
+  .tasks-board-group-header-sticky {
     position: sticky;
-    top: calc(
-      var(--tasks-board-column-header-height, 4rem)
-      + var(--tasks-board-stack-gap, 0.5rem)
-    );
-    z-index: 20;
+    top: 0;
+    z-index: 30;
+    background: var(--background);
+  }
+
+  .tasks-board-subcolumn-header-row {
     min-height: var(--tasks-board-subcolumn-header-height, 4rem);
+  }
+
+  .tasks-board-subcolumn-header-surface::after {
+    position: absolute;
+    right: -1px;
+    bottom: -0.75rem;
+    left: -1px;
+    height: 0.75rem;
+    border: 1px solid transparent;
+    border-top: 0;
+    border-radius: 0 0 0.75rem 0.75rem;
+    pointer-events: none;
+    background: transparent;
+    content: "";
+  }
+
+  .tasks-board-column-group[data-content-bottom-reached="true"] .tasks-board-subcolumn-header-surface::after {
+    border-color: var(--border-subtle);
+    border-top-color: transparent;
     background: var(--surface-secondary);
   }
 
   .tasks-board-lane-header {
     position: sticky;
-    top: calc(
-      var(--tasks-board-column-header-height, 4rem)
-      + var(--tasks-board-subcolumn-header-height, 4rem)
-      + var(--tasks-board-stack-gap, 0.5rem)
-      + var(--tasks-board-stack-gap, 0.5rem)
-    );
+    top: var(--tasks-board-group-header-stack-height, calc(9.5rem + 1px));
     z-index: 15;
     background: var(--surface-secondary);
   }
@@ -1043,4 +1087,5 @@ html[data-bs-theme="dark"] .shadow-xl {
     height: 3.9375rem;
     content: "";
   }
+
 }

frontend/src/app/tasks/page.tsx

@@ -1009,11 +1009,12 @@ function BoardColumn({
         isDragging ? "opacity-70" : ""
       }`}
     >
-      <div
-        className={`tasks-board-column-header app-surface flex min-h-16 items-center justify-between gap-3 rounded-xl px-3 py-3 transition ${columnBorderClass} ${
-          isDragging ? "shadow-xl" : ""
-        }`}
-      >
+      <div className={`tasks-board-column-header-sticky ${contentVisible ? "" : "tasks-board-column-header-sticky-standalone"}`}>
+        <div
+          className={`tasks-board-column-header app-surface flex min-h-16 items-center justify-between gap-3 rounded-xl px-3 py-3 transition ${columnBorderClass} ${
+            isDragging ? "shadow-xl" : ""
+          }`}
+        >
         <div
           ref={setActivatorNodeRef}
           className="min-w-0 flex-1 cursor-grab touch-none overflow-hidden active:cursor-grabbing"
@@ -1126,9 +1127,10 @@ function BoardColumn({
             ) : null}
           </div>
         </div>
+        </div>
       </div>
       {contentVisible ? <div
-        className={`tasks-column-scroll mt-2 min-h-0 flex-1 space-y-2 overflow-y-auto rounded-xl border bg-[var(--surface-primary)] p-3 transition xl:flex-none xl:overflow-visible ${columnBorderClass}`}
+        className={`tasks-column-scroll mt-2 min-h-0 flex-1 space-y-2 overflow-y-auto rounded-xl border bg-[var(--surface-primary)] p-3 transition xl:mt-0 xl:flex-none xl:overflow-visible ${columnBorderClass}`}
       >
         <TaskColumnCards
           tasks={tasks}
@@ -1209,14 +1211,16 @@ function BoardSubcolumnHeader({
     <section
       ref={setHeaderNodeRef}
       style={{
-        transform: sortable ? CSS.Transform.toString(transform) : undefined,
-        transition: sortable ? transition : undefined,
+        transform: sortable && synchronizedColumnDrag && transform
+          ? CSS.Transform.toString({ ...transform, y: 0 })
+          : undefined,
+        transition: sortable && synchronizedColumnDrag ? transition : undefined,
         zIndex: isDragging ? 20 : undefined,
       }}
       className={`flex w-full min-w-0 flex-col transition ${isDragging ? "opacity-70" : ""}`}
     >
       <div
-        className={`flex min-h-16 items-center justify-between gap-3 rounded-xl border bg-[var(--surface-primary)] px-3 py-3 shadow-sm transition ${columnBorderClass} ${
+        className={`tasks-board-subcolumn-header flex min-h-16 items-center justify-between gap-3 rounded-xl border bg-[var(--surface-primary)] px-3 py-3 shadow-sm transition ${columnBorderClass} ${
           isDragging ? "shadow-xl" : ""
         }`}
       >
@@ -1363,6 +1367,8 @@ function BoardColumnGroup({
   onColumnMount,
   contentVisible,
   onToggleContentVisibility,
+  subcolumnHeaders,
+  subcolumnGridTemplate,
   hideOnMobile = false,
 }: {
   column: TaskColumn;
@@ -1379,6 +1385,8 @@ function BoardColumnGroup({
   onColumnMount: (columnId: number, node: HTMLElement | null) => void;
   contentVisible: boolean;
   onToggleContentVisibility: () => void;
+  subcolumnHeaders: ReactNode;
+  subcolumnGridTemplate: string;
   hideOnMobile?: boolean;
 }) {
   const {
@@ -1408,14 +1416,15 @@ function BoardColumnGroup({
       }}
       className={`${hideOnMobile ? "hidden xl:flex" : "flex"} tasks-board-column-group min-w-0 flex-col ${isDragging ? "opacity-70" : ""}`}
     >
-      <div className="tasks-board-column-header app-surface flex min-h-16 items-center justify-between gap-3 rounded-xl px-3 py-3">
-        <div
-          ref={setActivatorNodeRef}
-          className="min-w-0 flex-1 cursor-grab touch-none active:cursor-grabbing"
-          title="Перетащите, чтобы изменить порядок колонок"
-          {...attributes}
-          {...listeners}
-        >
+      <div className="tasks-board-group-header-sticky">
+        <div className="tasks-board-column-header app-surface flex min-h-16 items-center justify-between gap-3 rounded-xl px-3 py-3">
+          <div
+            ref={setActivatorNodeRef}
+            className="min-w-0 flex-1 cursor-grab touch-none active:cursor-grabbing"
+            title="Перетащите, чтобы изменить порядок колонок"
+            {...attributes}
+            {...listeners}
+          >
           <div className="flex items-center gap-2">
             <span
               className="h-2.5 w-2.5 shrink-0 rounded-full"
@@ -1514,10 +1523,21 @@ function BoardColumnGroup({
               </div>
             ) : null}
           </div>
+          </div>
         </div>
+        {contentVisible ? (
+          <div className="tasks-board-subcolumn-header-surface relative mt-2 rounded-t-xl border border-b-0 border-[var(--border-subtle)] bg-[var(--surface-secondary)] p-2">
+            <div
+              className="tasks-board-subcolumn-header-row flex min-w-0 flex-col gap-2 xl:grid xl:w-max"
+              style={{ gridTemplateColumns: subcolumnGridTemplate }}
+            >
+              {subcolumnHeaders}
+            </div>
+          </div>
+        ) : null}
       </div>
       {contentVisible ? (
-        <div className="mt-2 flex w-full min-w-0 flex-col gap-2 rounded-xl border border-[var(--border-subtle)] bg-[var(--surface-secondary)] p-2 xl:w-auto xl:min-w-max">
+        <div className="tasks-board-column-content flex w-full min-w-0 flex-col gap-2 rounded-b-xl border border-t-0 border-[var(--border-subtle)] bg-[var(--surface-secondary)] px-2 pb-2 xl:w-auto xl:min-w-max">
           {children}
         </div>
       ) : null}
@@ -1550,7 +1570,7 @@ function BoardColumnRowView({
     <section className={`tasks-board-content-section min-w-0 ${
       hasFollowingSection ? "tasks-board-content-section-continuous" : ""
     }`}>
-      <div className={`tasks-board-lane-header flex items-center justify-between gap-3 px-1 ${expanded ? "mb-2" : ""}`}>
+      <div className={`tasks-board-lane-header flex items-center justify-between gap-3 px-1 ${expanded ? "mb-2 xl:mb-0 xl:pb-2" : ""}`}>
         <button
           type="button"
           onClick={onToggle}
@@ -1647,7 +1667,7 @@ function BoardBaseColumnsView({
         <button
           type="button"
           onClick={onToggle}
-          className={`tasks-board-lane-header flex w-full items-center gap-2 rounded-lg px-1 py-1 text-left ${headers ? "mt-2" : ""} ${expanded ? "mb-2" : ""}`}
+          className={`tasks-board-lane-header flex w-full items-center gap-2 rounded-lg px-1 py-1 text-left ${headers ? "mt-2" : ""} ${expanded ? "mb-2 xl:mb-0 xl:pb-2" : ""}`}
           aria-expanded={expanded}
         >
           <ChevronRight
@@ -3405,14 +3425,26 @@ function TasksPageContent() {
     const container = boardScrollRef.current;
     if (!container || loading) return undefined;
 
-    const updateViewportHeight = () => {
+    const updateBoardViewport = () => {
       setBoardViewportHeight(container.clientHeight);
+      container.querySelectorAll<HTMLElement>(".tasks-board-column-group").forEach((group) => {
+        const content = group.querySelector<HTMLElement>(".tasks-board-column-content");
+        const stickyHeader = group.querySelector<HTMLElement>(".tasks-board-group-header-sticky");
+        const contentBottomReached = content && stickyHeader
+          ? content.getBoundingClientRect().bottom <= stickyHeader.getBoundingClientRect().bottom + 1
+          : false;
+        group.dataset.contentBottomReached = contentBottomReached ? "true" : "false";
+      });
     };
-    updateViewportHeight();
+    updateBoardViewport();
 
-    const observer = new ResizeObserver(updateViewportHeight);
+    container.addEventListener("scroll", updateBoardViewport, { passive: true });
+    const observer = new ResizeObserver(updateBoardViewport);
     observer.observe(container);
-    return () => observer.disconnect();
+    return () => {
+      container.removeEventListener("scroll", updateBoardViewport);
+      observer.disconnect();
+    };
   }, [board?.id, desktopWideMode, loading]);
 
   useEffect(() => {
@@ -6954,29 +6986,7 @@ function TasksPageContent() {
                     );
                   }
 
-                  return (
-                    <BoardColumnGroup
-                      key={column.id}
-                      column={column}
-                      tasksCount={columnCounts.get(column.id) || 0}
-                      onCreateTask={() => {
-                        if (subcolumns[0]) startQuickTask(subcolumns[0].id);
-                        else startQuickTask(column.id);
-                      }}
-                      onCreateSubcolumn={() => openCreateColumn(column.id)}
-                      onCreateRow={() => openCreateColumnRow(column.id)}
-                      onEditColumn={openEditColumn}
-                      onDeleteColumn={deleteColumn}
-                      columnMenuOpen={columnMenuId === column.id}
-                      columnMenuRef={columnMenuRef}
-                      onToggleColumnMenu={() => toggleColumnMenu(column.id)}
-                      onColumnMount={registerColumnNode}
-                      contentVisible={!boardViewState.hidden_column_ids.includes(column.id)}
-                      onToggleContentVisibility={() => toggleBoardViewState("column", column.id)}
-                      hideOnMobile={hideOnMobile}
-                    >
-                      {(() => {
-                        const cellColumns = subcolumns.length ? subcolumns : [column];
+                  const cellColumns = subcolumns.length ? subcolumns : [column];
                         const activePreviewIndex = cellColumns.findIndex(
                           (item) => item.id === activeColumnDragId,
                         );
@@ -7068,41 +7078,55 @@ function TasksPageContent() {
                         ) : renderSubcolumnHeader(column, false);
 
                         return (
-                          <div className="flex min-w-0 flex-col gap-2 xl:w-max">
-                            <div
-                              className="tasks-board-subcolumn-header-row flex min-w-0 flex-col gap-2 xl:grid xl:w-max"
-                              style={{ gridTemplateColumns }}
-                            >
-                              {subcolumnHeaders}
-                            </div>
+                          <BoardColumnGroup
+                            key={column.id}
+                            column={column}
+                            tasksCount={columnCounts.get(column.id) || 0}
+                            onCreateTask={() => {
+                              if (subcolumns[0]) startQuickTask(subcolumns[0].id);
+                              else startQuickTask(column.id);
+                            }}
+                            onCreateSubcolumn={() => openCreateColumn(column.id)}
+                            onCreateRow={() => openCreateColumnRow(column.id)}
+                            onEditColumn={openEditColumn}
+                            onDeleteColumn={deleteColumn}
+                            columnMenuOpen={columnMenuId === column.id}
+                            columnMenuRef={columnMenuRef}
+                            onToggleColumnMenu={() => toggleColumnMenu(column.id)}
+                            onColumnMount={registerColumnNode}
+                            contentVisible={!boardViewState.hidden_column_ids.includes(column.id)}
+                            onToggleContentVisibility={() => toggleBoardViewState("column", column.id)}
+                            subcolumnHeaders={subcolumnHeaders}
+                            subcolumnGridTemplate={gridTemplateColumns}
+                            hideOnMobile={hideOnMobile}
+                          >
                             {baseColumns}
-                            <div className="flex min-w-0 flex-col gap-2">
-                              {columnRows.map((row, rowIndex) => {
-                                const rowTasksCount = filteredTasks.filter((task) => task.row === row.id).length;
-                                return (
-                                  <BoardColumnRowView
-                                    key={row.id}
-                                    row={{ ...row, tasks_count: rowTasksCount }}
-                                    gridTemplateColumns={gridTemplateColumns}
-                                    onCreateTask={() => {
-                                      if (cellColumns[0]) startQuickTask(cellColumns[0].id, row.id);
-                                    }}
-                                    onEdit={() => openEditColumnRow(row)}
-                                    onDelete={() => void deleteColumnRow(row)}
-                                    expanded={!boardViewState.collapsed_row_ids.includes(row.id)}
-                                    onToggle={() => toggleBoardViewState("row", row.id)}
-                                    hasFollowingSection={rowIndex < columnRows.length - 1}
-                                  >
-                                    {previewCellColumns.map((item) => renderTaskCell(item, row.id))}
-                                  </BoardColumnRowView>
-                                );
-                              })}
-                            </div>
-                          </div>
+                            {columnRows.length > 0 ? (
+                              <div className="flex min-w-0 flex-col gap-2">
+                                {columnRows.map((row, rowIndex) => {
+                                  const rowTasksCount = filteredTasks.filter((task) => task.row === row.id).length;
+                                  return (
+                                    <BoardColumnRowView
+                                      key={row.id}
+                                      row={{ ...row, tasks_count: rowTasksCount }}
+                                      gridTemplateColumns={gridTemplateColumns}
+                                      onCreateTask={() => {
+                                        if (cellColumns[0]) startQuickTask(cellColumns[0].id, row.id);
+                                      }}
+                                      onEdit={() => openEditColumnRow(row)}
+                                      onDelete={() => void deleteColumnRow(row)}
+                                      expanded={!boardViewState.collapsed_row_ids.includes(row.id)}
+                                      onToggle={() => toggleBoardViewState("row", row.id)}
+                                      hasFollowingSection={rowIndex < columnRows.length - 1}
+                                    >
+                                      {previewCellColumns.map((item) => renderTaskCell(item, row.id))}
+                                    </BoardColumnRowView>
+                                  );
+                                })}
+                              </div>
+                            ) : null}
+                          </BoardColumnGroup>
                         );
-                      })()}
-                    </BoardColumnGroup>
-                  );
                 })}
                 <AddColumnCard
                   onClick={() => openCreateColumn()}