fix(tool): stop defaulting manifest working_dir to /workspace

The /workspace compatibility symlink was removed from the manifest
compiler/entrypoint in 3e59a25. Tool definitions that still set
runtime.working_dir to /workspace therefore start in an empty directory
instead of /home/user/{repo_name}.

- manifest-editor.tsx: default working_dir to empty instead of /workspace;
  update startup-script placeholder to reference /home/alex/.
- Add Alembic migration 2026_06_19_113000 that clears the stale
  runtime.working_dir = /workspace from the built-in pi-agent manifest.
- Add migration import test.

Quality gates: pytest tests/api tests/services/test_terminal_manager_multi.py tests/unit (248 passed), ruff check (clean), npx tsc --noEmit (clean), eslint (clean).

.pi-map.index.md

@@ -16,7 +16,7 @@ dir: .
 Trust boundary: index routes, map orients, source decides.
 
 ## role
-Root configuration and documentation package for "Headquarter," a self-hosted project management platform with Git repository features, containing deployment configs, development tooling, and UI rework tracking documents.
+Infrastructure and configuration package for "Headquarter," a self-hosted project management platform with Git repository features, containing deployment configs, development tooling, and UI refactoring documentation.
 ## parent
 -
 ## children
@@ -77,7 +77,6 @@ Root configuration and documentation package for "Headquarter," a self-hosted pr
 - README.md
 - docker-compose.traefik.yml
 - docker-compose.yml
-- package-lock.json
 - progress.md
 - swap-pane
 - ui-audit-spacing-typography.md