## What changed
- Add the experimental `turn/settings/update` method for changing `model`,
`effort`, `summary`, and `serviceTier` on a specific live turn without
changing future turns.
- Report whether the update was applied or the target turn was unavailable,
and reject unsupported fields, disabled feature use, unsafe model changes,
and direct updates to parent-owned subagents.
- Document the method's feature requirements, null handling, and limits.
## Testing
- Cover current-turn and future-turn isolation, rejected and unavailable
targets, feature and capability gates, saved threads, and subagent ownership.
GitOrigin-RevId: 18440f6d7ee5fcd06ae23bd41b22c492b62bb2b5
