Add persisted thread pinning to the app server (#34840)

## What changed

- Add `isPinned` to thread responses and allow `thread/metadata/update` to pin or unpin stored threads.
- Add an `isPinned` filter to `thread/list`, including cursor-based pagination and combinations with relationship filters.
- Persist pin state in SQLite without modifying rollout files, default existing threads to unpinned, and preserve pins through reconciliation and archive transitions.

## Testing

- Cover protocol serialization, database migration and indexing, pin updates, filtered pagination, rollout reconciliation, and archive/unarchive behavior.

GitOrigin-RevId: c2eacabd6dae465e2ae6ce8a169e00740960cdb7

codex-rs/thread-store/src/local/archive_thread.rs

@@ -108,6 +108,7 @@ mod tests {
                 allowed_sources: Vec::new(),
                 model_providers: None,
                 cwd_filters: None,
+                is_pinned: None,
                 archived: true,
                 search_term: None,
                 relation_filter: None,