Register PersistentSessionService in the DI Container so that
'agents session list' (and all other session subcommands) no longer
throw AttributeError due to a missing 'db' provider.
Changes:
- Add _build_session_service() factory and session_service provider to
Container, with targeted table creation for session/session_messages
only (avoids bypassing Alembic for the full schema).
- Add auto_commit parameter to SessionRepository and
SessionMessageRepository; when True each method commits and closes
its own database session, preventing resource leaks in CLI context.
- Rewrite _get_session_service() to resolve via container.session_service()
with module-level caching.
- Add (DatabaseError, AttributeError) error handling with logging to all
seven session subcommands (list, create, show, delete, export, import,
tell).
- Remove @tdd_expected_fail tags from all session test files so they run
as proper regression tests.
ISSUES CLOSED: #554, #570, #680
brent.edwards
freemo