## What changed
- Add optional `icon` and `color` appearance fields to custom thread sections and expose them through the app-server protocol.
- Persist appearance metadata in SQLite and include it when listing sections or returning threads.
- Let `threadSection/update` preserve an omitted appearance, clear it with `null`, or replace it with a new value.
- Reject appearance fields larger than 64 bytes.
## Testing
- Cover protocol compatibility, persistence across restart, update and clear behavior, and field-length validation.
GitOrigin-RevId: 8f55ce4f42f8bd17aa5416848a85845f681953df
1549756b78