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/services/tool/instance_service.py

@@ -13,7 +13,8 @@ from fastapi import HTTPException, status
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from src.models import ConfigProfile, GitRepository, SSHKey, ToolInstance, ToolType
+from src.models import ConfigProfile, GitRepository, Project, SSHKey, ToolInstance, ToolType
+from src.schemas.tool import CreateInstanceRequest, StartInstanceRequest
 from src.services.git.clone import check_dirty_state, clone_repository
 from src.services.config.config_profile_resolver import (
     ConfigProfileCycleError,
@@ -935,8 +936,10 @@ async def create_tool_instance(
     if data.display_name:
         instance_display = data.display_name
     else:
+        project = await session.get(Project, project_id)
+        project_name = project.name if project else "Unknown"
         scope_name = workspace.name if workspace else repo.name
-        auto_name = f"{scope_name} / {tool_type.display_name}"
+        auto_name = f"{project_name} / {scope_name} / {tool_type.display_name}"
 
         if workspace:
             count_query = (
@@ -2161,3 +2164,25 @@ async def stop_tool_instance(
         message="Instance stopped",
     )
     return {"status": instance.status}
+
+
+async def rename_tool_instance(
+    session: AsyncSession,
+    user_id: uuid.UUID,
+    project_id: uuid.UUID,
+    repo_id: uuid.UUID,
+    instance_id: uuid.UUID,
+    display_name: str,
+) -> ToolInstance:
+    """Rename a tool instance (update display_name only)."""
+    instance = await session.get(ToolInstance, instance_id)
+    if instance is None or instance.repository_id != repo_id:
+        raise ValueError("instance not found")
+    if instance.owner_id != user_id:
+        raise ValueError("not authorized")
+
+    instance.display_name = display_name.strip()
+    await session.commit()
+    await session.refresh(instance)
+    return instance
+