## What changed
- Replace `send_user_message_async` with `request_user_input_async`, accepting one or more questions with optional suggested answers while allowing the turn to continue.
- Attach structured question metadata to asynchronous agent messages while retaining readable fallback text, and preserve it through app-server events, thread history, and generated schemas.
- Continue enabling the new tool for model catalogs that advertise either the old or new tool name.
## Testing
- Cover tool registration, question validation, emitted items, continued turn execution, history preservation, and backwards-compatible deserialization.
GitOrigin-RevId: ffc49aebde2e854c3c50a122aa52805fec3fc6b3
## What changed
- Add an optional `toolOutput` to `turn/start` for starting or steering a turn with a named function-call output instead of user input.
- Emit standalone outputs as `functionCallOutput` thread items, persist them in durable history, and include them in resumed threads.
- Validate that tool outputs have a name, are not combined with nonempty `input`, satisfy the text-size limit, and use supported image URLs.
## Testing
- Cover standalone tool-output notifications, model input, and resumed history in both legacy and paginated history modes.
- Cover the text-size limit for structured tool output.
GitOrigin-RevId: a1eeec7b9b7de67b1a1c5e829a54552b85ec118b
## What changed
- Make `thread/turns/list`, `thread/items/list`, and `thread/revert` available
without the experimental API capability.
- Stabilize `thread/reverted`, `thread.historyMode`, and the pagination fields
used by `thread/resume` and `thread/fork`.
- Publish the promoted requests, responses, and fields in the stable JSON and
TypeScript schemas, and update the app-server documentation accordingly.
GitOrigin-RevId: 18b8c53c265211597bb1a62fd62f66f4a3df5f06
