feat: improve session naming, project display, rename support, tab titles

Backend:
- sessions.py: include workspace_name in session response
- instance_service.py: auto-generate display names as
  'Project / Workspace / Tool #N' instead of 'Workspace / Tool #N'
- instance_service.py: add rename_tool_instance() service function
- tool_instances.py: add PATCH /instances/{id} endpoint for renaming
  display_name

Frontend:
- api/sessions.ts: add workspace_name to Session type, add renameInstance()
- use-instance-actions.ts: add handleRename, set document.title when opening
- session-card.tsx: click-to-edit display_name inline; always show project
  context line (Project / Workspace or Repo / Tool)
- session-list.tsx: pass through onRename prop
- SessionsPage.tsx: wire handleRename to SessionCard and SessionList
- app-shell.tsx: sidebar tooltip includes workspace or repo name
- use-terminal-page.ts: set document.title based on active terminal session

Quality gates: py_compile all backend files pass, tsc --noEmit pass,
npm run build pass, 82/82 tests pass

apps/web/src/hooks/use-terminal-page.ts

@@ -61,6 +61,20 @@ export const useTerminalPage = () => {
     }
   }, [loading, sessions.length, error, instanceId, createSession]);
 
+  // Update document title based on active terminal session
+  useEffect(() => {
+    if (!instanceId) {
+      document.title = "Terminal — Headquarter";
+      return;
+    }
+    const active = sessions.find((s) => s.id === activeSessionId);
+    const name = active?.name ?? `Instance ${instanceId.slice(0, 8)}`;
+    document.title = `${name} — Terminal — Headquarter`;
+    return () => {
+      document.title = "Headquarter";
+    };
+  }, [instanceId, activeSessionId, sessions]);
+
   // Sync refs with sessions
   useEffect(() => {
     for (const session of sessions) {