feat: complete working-copies workspace-first cleanup

- Remove clone_mode/branch/new_branch from frontend create session flow.
- Add workspace picker to CreateSessionForm; auto-create default workspace when repo selected.
- Fix tool-starter.tsx and use-start-tool.ts createInstance signatures after API change.
- Remove clone mode badge from SessionCard.
- Delete stale backend unit tests referencing removed clone_mode schema fields.
- Update OpenSpec working-copies tasks and mark change completed.
- Regenerate project maps.

Quality gates: npm run typecheck, npm run lint, npm test -- --run (82 passed),
python3 -m py_compile on changed backend files.

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 reusable React components that implement specific product features and business logic for the web application.
+Contains specialized UI components for major feature areas of the web application, organizing components by business domain rather than by atomic design level.
 ## files
 ## arch
-Feature-based component organization with domain-specific UI building blocks, likely composed of atomic design elements (from components/ui) and consumed by page-level routes.
+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.
 ## tags
 -
 ## symbols