feat: implement configurable tool container home directory

- Add ToolType.home_directory column with default /home/user
- Add Alembic migration to add column, set existing rows, and rewrite
  /workspace to /home/user/{{WORKSPACE_NAME}} in legacy templates
- Add merge migration fc8f1a20cbf6 to resolve Alembic multiple heads
- Update manifest compiler to honor manifest.home_directory for HOME,
  WORKDIR, /workspace symlink, and default repo mount target
- Update legacy dockerfile/compose instance generation to use
  tool_type.home_directory
- Thread resolved home_dir through config profile and git mount expansion
- Generate entrypoint permission fixer to chown home/mounts at startup
- Update base.dockerfile with sudo/passwordless sudo for permission fixer
- Add unit tests for manifest compiler, instance service, and migrations
- Add placeholder integration test for container lifecycle
- Update openspec/tasks/home-path-expansion.md task checkboxes
- Update project maps for modified files

Quality gates: py_compile, ruff, mypy, pytest tests/unit (205 passed),
pytest tests/integration (110 passed, 35 skipped). Alembic round-trip
and container lifecycle integration tests require Docker/PostgreSQL.

docs/superpowers/.pi-map.index.md

@@ -2,11 +2,14 @@
 dir: docs/superpowers
 
 ## role
-Documentation for advanced or specialized features and capabilities of the project.
+Documentation for specialized capabilities or advanced features of the project.
 ## parent
 index: docs/.pi-map.index.md
 map: docs/.pi-map.md
 ## children
+- docs/superpowers/handoffs
+  index: docs/superpowers/handoffs/.pi-map.index.md
+  map: docs/superpowers/handoffs/.pi-map.md
 - docs/superpowers/plans
   index: docs/superpowers/plans/.pi-map.index.md
   map: docs/superpowers/plans/.pi-map.md