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.

apps/api/tests/unit/.pi-map.index.md

@@ -2,7 +2,7 @@
 dir: apps/api/tests/unit
 
 ## role
-Contains comprehensive unit tests for the API backend services covering configuration, Docker operations, Git integration, file management, health monitoring, notifications, and SSH key handling.
+Unit test suite for the API application covering core services, utilities, and infrastructure components.
 ## parent
 index: apps/api/tests/.pi-map.index.md
 map: apps/api/tests/.pi-map.md
@@ -10,6 +10,7 @@ map: apps/api/tests/.pi-map.md
 -
 ## files
 - __init__.py
+- test_alembic_migrations.py
 - test_config.py
 - test_config_profile_resolver.py
 - test_docker_build.py
@@ -21,6 +22,7 @@ map: apps/api/tests/.pi-map.md
 - test_git_url_parser.py
 - test_health_monitor.py
 - test_home_path_expansion.py
+- test_instance_service.py
 - test_lifecycle_hooks.py
 - test_manifest_compiler.py
 - test_migration_metadata.py
@@ -35,7 +37,7 @@ index: apps/api/tests/unit/.pi-map.index.md
 map: apps/api/tests/unit/.pi-map.md
 ## workflows
 - change unit behavior
-  read: __init__.py, test_config.py, test_config_profile_resolver.py
+  read: __init__.py, test_alembic_migrations.py, test_config.py
 - change unit config
   read: test_config.py, test_config_profile_resolver.py
 ## dirty