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/web/src/pages/RepoWorkspacePage.tsx

@@ -198,7 +198,7 @@ export const RepoWorkspace = () => {
 						)}
 						<main className="workspace-main">
 							{selectedRepoId && (
-								<FileEditor projectId={projectId!} repoId={selectedRepoId} />
+								<FileEditor projectId={projectId!} repoId={selectedRepoId} gitStatus={gitStatus} />
 							)}
 						</main>
 					</div>