## 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
## What changed
- Replace the `isPinned` thread metadata and filters with an optional persisted
`section` and `sectionId`.
- Add the paginated `threadSection/list` app-server method so clients can
discover sections even when they contain no threads.
- Seed a stable `Pinned` section, validate section assignments, and support
filtering for a specific section or for unsectioned threads.
## Testing
- Cover section protocol serialization, listing and pagination, metadata
updates, filtering, persistence, migration compatibility, and operation
without SQLite state.
GitOrigin-RevId: 7972b5471d29317b9387bfd90aa9f573f691ad4c
