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/web/src/components/features/.pi-map.md

@@ -4,10 +4,10 @@ dir: apps/web/src/components/features
 index: apps/web/src/components/features/.pi-map.index.md
 
 ## role
-Contains specialized UI components for major feature areas of the web application, organizing components by business domain rather than by atomic design level.
+Contains reusable React components that implement specific user-facing functionality and business logic features across the web application.
 ## files
 ## arch
-Feature-based colocation pattern where components are grouped by product functionality (e.g., checkout, dashboard, settings) rather than by component type, typically combining multiple atomic components with domain-specific logic and data fetching.
+Feature-based component organization with domain-specific grouping, likely using composition patterns and co-located feature logic (hooks, utils, sub-components) following a modular frontend architecture.
 ## tags
 -
 ## symbols