* Improve the web launcher and gateway integration across backend and frontend.
- 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
* feat(agent): add skills and tools management APIs and UI
- add backend APIs to list, view, import, and delete skills
- add tool status and toggle endpoints with dependency-aware config updates
- add agent skills/tools pages, routes, sidebar entries, and i18n strings
- add backend tests for the new skills and tools flows
* chore(frontend): upgrade shadcn to 4.0.5 and refresh lockfile
* chore(web): keep backend dist placeholder tracked
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