fix(graphrag): crash on project rename/path change (DF-009)

session_events.py::_on_projects_changed (runs on every project
create/rename/delete) called self.structure._refresh_project_combo() —
but that method only ever existed on GraphRenderer, not on
StructureGraphView itself (self.structure). Renaming a project or
changing its working-directory path raised AttributeError and crashed
the app.

Add StructureGraphView.refresh_project_list(), matching the existing
schedule_rescan/set_project/prewarm forwarding pattern, and call that
instead. Add a regression test
(test_refresh_project_list_forwards_to_renderer).

Logged as DF-009 in Task Tracking Template.xlsx — root cause, fix and
regression test recorded (row was empty in this local copy despite
being reported as already logged there).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

presentation/graph/structure_graph_view.py

@@ -219,6 +219,12 @@ class StructureGraphView(QWidget):
         """Dựng sẵn khung đồ thị trước khi người dùng bấm vào, để lần mở đầu không giật."""
         self.renderer.prewarm()
 
+    def refresh_project_list(self) -> None:
+        """Project khác vừa được tạo/sửa/xoá/đổi tên — làm mới danh sách trong
+        bộ chọn project của renderer (bộ chọn KHÔNG tự nạp lại khi project
+        thay đổi ở màn khác, chỉ khi ``set_project`` được gọi)."""
+        self.renderer._refresh_project_combo()
+
     def hideEvent(self, e):  # noqa: N802
         # Leaving the GraphRAG tab → drop the temporary extracted info.
         """Rời màn GraphRAG thì xoá phần trích xuất tạm của khung hỏi-đáp."""