Add new empty scheme creation action and support empty JSON load

- Добавлено действие Создать... (Ctrl+N) в меню Файл для инициализации нового файла схемы.
- Реализована автоматическая запись дефолтной схемы circles при открытии пустого или содержащего только пробелы json-файла.
- Добавлены соответствующие автоматические тесты в qa_smoke.py.

main_window.py

@@ -336,6 +336,7 @@ class MainWindow(QMainWindow):
             self.actions[key] = action
             return action
 
+        add_action("new", "Создать...", self.new_file, "file-plus", QKeySequence.New)
         add_action("open", "Открыть", self.open_file, "folder-open", QKeySequence.Open)
         add_action("save", "Сохранить", self.save_file, "save", QKeySequence.Save)
         add_action("save_as", "Сохранить как", self.save_file_as, "save-all", QKeySequence.SaveAs)
@@ -446,6 +447,7 @@ class MainWindow(QMainWindow):
         menu_bar = self.menuBar()
         menu_bar.clear()
         file_menu = menu_bar.addMenu("Файл")
+        file_menu.addAction(self.actions["new"])
         file_menu.addAction(self.actions["open"])
         file_menu.addAction(self.actions["save"])
         file_menu.addAction(self.actions["save_as"])
@@ -904,6 +906,43 @@ class MainWindow(QMainWindow):
             action.setText("Скрыть боковую панель")
             action.setToolTip("Скрыть боковую панель")
 
+    def new_file(self) -> None:
+        if not self._confirm_discard_changes():
+            return
+        path, _ = QFileDialog.getSaveFileName(
+            self,
+            "Создать новую схему",
+            str(APP_DIR),
+            "JSON files (*.json);;All files (*.*)",
+        )
+        if not path:
+            return
+        p = Path(path)
+        if not p.suffix:
+            p = p.with_suffix(".json")
+        try:
+            p.write_text('{"circles": []}', encoding="utf-8")
+        except Exception as exc:
+            show_critical(self, "Ошибка создания файла", str(exc))
+            return
+        loaded = MappingDocument()
+        try:
+            loaded.load(p)
+        except Exception as exc:
+            show_critical(self, "Ошибка загрузки нового файла", str(exc))
+            return
+        self.document = loaded
+        self._dirty = False
+        self._undo_stack.clear()
+        self._redo_stack.clear()
+        self.active_line_id = None
+        self.canvas.set_document(self.document)
+        self.canvas.set_active_line(self.active_line_id)
+        self.refresh_tree()
+        self._sync_canvas_to_active_line()
+        self.status.setText(f"Создана новая пустая схема: {p}")
+        self._refresh_ui_state()
+
     def open_file(self) -> None:
         if not self._confirm_discard_changes():
             return

models.py

@@ -43,6 +43,16 @@ _LED_POINT_KNOWN_FIELDS = {
 
 def load_json_document(path: str | Path) -> dict[str, Any]:
     path = Path(path)
+    if path.exists():
+        try:
+            if path.stat().st_size == 0:
+                path.write_text('{"circles": []}', encoding="utf-8")
+            else:
+                content = path.read_bytes()
+                if not content.strip():
+                    path.write_text('{"circles": []}', encoding="utf-8")
+        except Exception:
+            pass
     text, was_converted = _read_text_as_utf8(path)
     if was_converted:
         path.write_text(text, encoding="utf-8")

qa_smoke.py

@@ -69,6 +69,13 @@ except ImportError:
     QDialogButtonBox = None
     QGraphicsItem = None
     QMessageBox = None
+    QColor = None
+    QImage = None
+    QKeySequence = None
+    QApplication = None
+    QDialogButtonBox = None
+    QGraphicsItem = None
+    QMessageBox = None
     QToolBar = None
 
 
@@ -77,6 +84,7 @@ PROJECT_ROOT = Path(__file__).resolve().parent.parent
 
 def main() -> None:
     tests: list[Callable[[], None]] = [
+        test_load_empty_json_file,
         test_load_supported_json_files,
         test_load_raw_json_with_trailing_commas_and_bare_decimal_points,
         test_non_utf8_json_is_converted_to_utf8_on_load,
@@ -121,6 +129,7 @@ def main() -> None:
         test_panel_mapping_generation_with_strategies,
         test_block_renaming_and_naming_strategy,
         test_line_renaming_and_tree_shortcuts,
+        test_new_file_action,
         test_export_mapping_to_image,
         test_save_preserves_unknown_source_fields,
         test_ordered_json_preserves_document_and_remaps_uids,
@@ -221,6 +230,25 @@ def main() -> None:
     print(f"All {len(tests)} QA smoke checks passed.")
 
 
+def test_load_empty_json_file() -> None:
+    with tempfile.TemporaryDirectory() as temp_dir:
+        # Test 1: Completely empty file (0 bytes)
+        path = Path(temp_dir) / "empty.json"
+        path.write_bytes(b"")
+        doc = MappingDocument()
+        doc.load(path)
+        assert len(doc.points) == 0
+        assert path.read_text(encoding="utf-8") == '{"circles": []}'
+
+        # Test 2: Whitespace-only file
+        path_ws = Path(temp_dir) / "whitespace.json"
+        path_ws.write_text("   \n  \t ", encoding="utf-8")
+        doc_ws = MappingDocument()
+        doc_ws.load(path_ws)
+        assert len(doc_ws.points) == 0
+        assert path_ws.read_text(encoding="utf-8") == '{"circles": []}'
+
+
 def test_load_supported_json_files() -> None:
     fixtures = [
         PROJECT_ROOT / "circles.json",
@@ -1132,6 +1160,31 @@ def test_line_renaming_and_tree_shortcuts() -> None:
     
     window.close()
 
+def test_new_file_action() -> None:
+    if MainWindow is None or QApplication is None:
+        return
+    app = QApplication.instance() or QApplication([])
+    window = MainWindow()
+
+    from PySide6.QtWidgets import QFileDialog
+    with tempfile.TemporaryDirectory() as temp_dir:
+        new_path = Path(temp_dir) / "created_scheme.json"
+
+        original_getSaveFileName = QFileDialog.getSaveFileName
+        QFileDialog.getSaveFileName = lambda *args, **kwargs: (str(new_path), "JSON files (*.json)")
+        try:
+            window.new_file()
+        finally:
+            QFileDialog.getSaveFileName = original_getSaveFileName
+
+        assert new_path.exists()
+        assert new_path.stat().st_size > 0
+        assert len(window.document.points) == 0
+        assert window.document.path == new_path
+
+    window.close()
+
+
 
 def test_export_mapping_to_image() -> None:
     if QApplication is None:
@@ -1856,6 +1909,11 @@ def test_canvas_refresh_does_not_accumulate_connection_items() -> None:
     assert len(canvas.items_by_id) == len(doc.points)
 
 
+def test_main_window_has_classic_menu_bar() -> None:
+    if MainWindow is None or QApplication is None:
+        return
+    app = QApplication.instance() or QApplication([])
+    window = MainWindow()
 def test_main_window_has_classic_menu_bar() -> None:
     if MainWindow is None or QApplication is None:
         return
@@ -1877,7 +1935,7 @@ def test_classic_menu_contains_expected_actions() -> None:
     app.processEvents()
 
     expected = {
-        "Файл": ["Открыть", "Сохранить", "Сохранить как", "Сгенерировать скрипт", "Параметры"],
+        "Файл": ["Создать...", "Открыть", "Сохранить", "Сохранить как", "Сгенерировать скрипт", "Параметры"],
         "Правка": ["Отменить", "Повторить", "Удалить фиксацию", "Удалить точки", "Удалить все", "Очистить выбор"],
         "Вид": [
             "Показать всё",
@@ -1974,6 +2032,7 @@ def test_main_window_actions_use_lucide_icons() -> None:
     app.processEvents()
 
     expected_icon_actions = {
+        "new",
         "open",
         "save",
         "save_as",
@@ -2017,6 +2076,7 @@ def test_main_window_action_shortcuts_are_assigned() -> None:
     app.processEvents()
 
     expected = {
+        "new": "Ctrl+N",
         "generate_script": "Ctrl+G",
         "settings": "Ctrl+,",
         "delete_points": "Ctrl+Del",