fix: use sudo/root to create /workspace symlink in manifest entrypoint

The previous commit moved the pi-agent repo mount from /workspace to
/home/user/{repo_name}. This exposed a permission bug: the Dockerfile
creates /workspace as a root-owned symlink in the image, and the
non-root entrypoint could not replace it because / is owned by root.

- Update compile_entrypoint to recreate /workspace via sudo when running
  as the container user, or directly when running as root
- Add unit test covering sudo/root symlink creation
- Update OpenSpec change docs with the additional root cause

Quality gates:
- pytest tests/unit: 208 passed
- ruff: clean on changed files
- mypy: clean on changed files
- alembic heads: single head

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

@@ -2,12 +2,14 @@
 dir: apps/api/tests/unit
 
 ## role
-Contains unit tests for the API application's core services, utilities, and infrastructure components.
+Unit test suite for the API application covering configuration, database migrations, Docker operations, Git integration, file services, monitoring, notifications, and manifest compilation.
 ## parent
 index: apps/api/tests/.pi-map.index.md
 map: apps/api/tests/.pi-map.md
 ## children
--
+- apps/api/tests/unit/.ruff_cache
+  index: apps/api/tests/unit/.ruff_cache/.pi-map.index.md
+  map: apps/api/tests/unit/.ruff_cache/.pi-map.md
 ## files
 - __init__.py
 - test_alembic_migrations.py
@@ -40,5 +42,7 @@ map: apps/api/tests/unit/.pi-map.md
   read: __init__.py, test_alembic_migrations.py, test_config.py
 - change unit config
   read: test_config.py, test_config_profile_resolver.py
+- explore unit subdirectories
+  index: apps/api/tests/unit/.ruff_cache/.pi-map.index.md
 ## dirty
 -