fix: resolve four frontend/backend issues

- Fix ProjectsPage tests by wrapping renders in MemoryRouter (9 passing)
- Improve session auto-naming to 'project / repo / tool' format
- Add missing /users/me/sessions endpoint for sidebar session loading
- Handle git history 500s: catch RuntimeError in endpoints, graceful empty repo handling
- Add git status badge and discard-changes button to FileEditor toolbar

Quality gates: tsc pass, build pass, Python syntax pass

apps/api/src/services/instance_lifecycle.py

@@ -54,7 +54,7 @@ async def create_new_instance(
 
     instance = ToolInstance(
         name=instance_name,
-        display_name=display_name or f"{tool_type.display_name} - {repo.name}",
+        display_name=display_name or f"{project.name} / {repo.name} / {tool_type.display_name}",
         tool_type_id=tool_type.id,
         repository_id=repo.id,
         project_id=project.id,