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/api/src/api/tool/sessions.py

@@ -53,6 +53,13 @@ async def get_user_sessions(
         repo = await session.get(GitRepository, instance.repository_id)
         project = await session.get(Project, instance.project_id)
 
+        workspace_name = None
+        if instance.workspace_id:
+            from src.models import Workspace as WorkspaceModel
+            workspace = await session.get(WorkspaceModel, instance.workspace_id)
+            if workspace:
+                workspace_name = workspace.name
+
         sessions.append(
             {
                 "id": str(instance.id),
@@ -64,6 +71,7 @@ async def get_user_sessions(
                 "repository_id": str(instance.repository_id),
                 "project_name": project.name if project else "unknown",
                 "project_id": str(instance.project_id),
+                "workspace_name": workspace_name,
                 "status": instance.status,
                 "url": instance.url,
                 "clone_mode": instance.clone_mode,

apps/api/src/api/tool/tool_instances.py

@@ -29,6 +29,7 @@ from src.services.tool.instance_service import (
     create_tool_instance,
     delete_tool_instance,
     recreate_instance_tunnel,
+    rename_tool_instance,
     restart_tool_instance,
     start_tool_instance,
     stop_tool_instance,
@@ -153,6 +154,45 @@ async def get_instance(
     }
 
 
+@router.patch(
+    "/{project_id}/repositories/{repo_id}/instances/{instance_id}",
+    summary="Rename instance",
+    description="Update the display name of a tool instance.",
+)
+async def rename_instance(
+    project_id: uuid.UUID,
+    repo_id: uuid.UUID,
+    instance_id: uuid.UUID,
+    data: dict,
+    user_id: uuid.UUID = Depends(get_current_user_id),
+    session: AsyncSession = Depends(get_db_session),
+) -> dict:
+    _user = await _get_user(session, user_id)
+    _project = await _get_owned_project(project_id, user_id, session)
+
+    display_name = data.get("display_name", "").strip()
+    if not display_name:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="display_name is required",
+        )
+
+    try:
+        instance = await rename_tool_instance(
+            session, user_id, project_id, repo_id, instance_id, display_name
+        )
+    except ValueError as exc:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail=str(exc)
+        )
+
+    return {
+        "id": str(instance.id),
+        "name": instance.name,
+        "display_name": instance.display_name,
+    }
+
+
 @router.post(
     "/{project_id}/repositories/{repo_id}/instances/{instance_id}/start",
     summary="Start instance",