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/tests/integration/.pi-map.index.md

@@ -2,7 +2,7 @@
 dir: apps/api/tests/integration
 
 ## role
-Integration and unit test suite for the API backend, covering authentication, REST endpoints, database models, and core services with real database dependencies.
+Integration and unit test suite for the FastAPI backend API, covering authentication, CRUD APIs, workspace/git operations, and event/notification systems using real databases and external dependencies.
 ## parent
 index: apps/api/tests/.pi-map.index.md
 map: apps/api/tests/.pi-map.md
@@ -24,6 +24,9 @@ map: apps/api/tests/.pi-map.md
 - test_tool_types_api.py
 - test_tool_types_api_extended.py
 - test_users_api.py
+- test_workspace_files.py
+- test_workspace_git.py
+- test_workspace_instances.py
 - test_workspaces_api.py
 ## links
 index: apps/api/tests/integration/.pi-map.index.md