The API server adapter created AIAgent instances without passing
session_db, so conversations via Open WebUI and other OpenAI-compatible
frontends were never persisted to state.db. This meant 'hermes sessions
list' showed no API server sessions — they were effectively stateless.
Changes:
- Add _ensure_session_db() helper for lazy SessionDB initialization
- Pass session_db=self._ensure_session_db() in _create_agent()
- Refactor existing X-Hermes-Session-Id handler to use the shared helper
Sessions now persist with source='api_server' and are visible alongside
CLI and gateway sessions in hermes sessions list/search.