- add runtime model availability checks for local and OAuth-backed models
- support launcher-driven gateway host overrides and websocket URL resolution
- add gateway log clearing and keep incremental log sync consistent after resets
- migrate session history APIs to JSONL metadata-backed storage with legacy fallback
- expose session titles and improve chat history loading and error handling
- move shared backend runtime helpers into the web utils package
- avoid blocking web startup when automatic onboard initialization fails
- add backend tests covering gateway readiness, host resolution, models, logs, and sessions
