feat: complete workspace-first-ui cleanup and tests

- Delete dead repo-workspace code: RepoWorkspacePage, useRepoWorkspace,
  WorkspaceLayout, FileBrowser, old git components (git-toolbar, file-editor,
  commit-panel), and repo-workspace.css.
- Fix stale backend test imports for moved models/services.
- Add GitOperations unit tests.
- Add integration tests for workspace files, git, and instances endpoints.
- Add frontend tests for WorkspaceDetailPage and ProjectCard.
- Update OpenSpec workspace-first-ui tasks and mark change completed.
- Regenerate project maps.

Quality gates: npm run typecheck, npm run lint, npm test -- --run (87 passed),
python3 -m py_compile on changed backend files, pytest backend workspace tests.

apps/api/.pi-map.index.md

@@ -2,7 +2,7 @@
 dir: apps/api
 
 ## role
-Backend API server providing project management, git repository operations, and development tool orchestration via Docker containers.
+Self-hosted FastAPI backend API that manages projects, git repositories, and development tools via Docker instances.
 ## parent
 index: apps/.pi-map.index.md
 map: apps/.pi-map.md
@@ -10,6 +10,12 @@ map: apps/.pi-map.md
 - apps/api/.pi-lens
   index: apps/api/.pi-lens/.pi-map.index.md
   map: apps/api/.pi-lens/.pi-map.md
+- apps/api/.pytest_cache
+  index: apps/api/.pytest_cache/.pi-map.index.md
+  map: apps/api/.pytest_cache/.pi-map.md
+- apps/api/.venv-test
+  index: apps/api/.venv-test/.pi-map.index.md
+  map: apps/api/.venv-test/.pi-map.md
 - apps/api/alembic
   index: apps/api/alembic/.pi-map.index.md
   map: apps/api/alembic/.pi-map.md