chore: checkpoint current performance and UI changes

presentation/shell/main_window.py

@@ -32,9 +32,7 @@ from .rail_metrics import _NAV_MIN_WIDTH
 from .tray_manager import TrayManager
 from ...state import AppContext
 from ...core.task_scheduler import TaskScheduler
-from ...ui.cowork_tab import CoworkTab
 from ...ui.sidebar import HistorySidebar
-from ..graph.structure_graph_view import StructureGraphView
 from ...ui.workspace_tab import WorkspaceTab
 
 
@@ -111,10 +109,9 @@ class MainWindow(NavRailMixin, RailProjectMixin, TopBarMixin,
         # Workspace screen (per selected project). GraphRAG's heavy
         # QtWebEngine is still built lazily on first display
         # (StructureGraphView._ensure_web).
+        from ...ui.cowork_tab import CoworkTab
         self.cowork = CoworkTab(ctx)
-        self.structure = StructureGraphView(ctx)
-        self.structure.status_message.connect(self.statusBar().showMessage)
-        self.cowork.output_changed.connect(self.structure.schedule_rescan)
+        self.structure = None
         self.cowork.status_message.connect(self.statusBar().showMessage)
         # Refresh History (list + running markers + current highlight) whenever a
         # conversation is created/updated or a turn finishes.

presentation/shell/session_events.py

@@ -42,7 +42,14 @@ class SessionEventsMixin:
             self.sidebar.refresh()
             self._refresh_rail_recents()   # the rail shortcut follows the panel
 
-        QTimer.singleShot(0, _do)
+        # Coalesce bursts from turn/tool/history signals into one sidebar read.
+        timer = getattr(self, "_history_refresh_timer", None)
+        if timer is None:
+            timer = QTimer(self)
+            timer.setSingleShot(True)
+            timer.timeout.connect(_do)
+            self._history_refresh_timer = timer
+        timer.start(0)
     def _on_scheduled_task_done(self, task_id: str, ok: bool) -> None:
         """Desktop notification for a finished scheduled task (toast always,
         tray balloon when the window isn't focused), then refresh History —
@@ -106,4 +113,5 @@ class SessionEventsMixin:
         """Project được tạo/sửa/xoá: gom nhóm lại cột lịch sử và cập nhật nhãn thư mục."""
         self.sidebar.refresh()                 # History regroups by project
         self.cowork._apply_output_folder_label()  # project may have been renamed
-        self.structure._refresh_project_combo()   # GraphRAG's project lock list follows too
+        if getattr(self, "structure", None) is not None:
+            self.structure._refresh_project_combo()   # GraphRAG's project lock list follows too