## Why
Paginated threads need explicit user-facing names to remain distinct from
derived titles and previews without requiring rollout metadata writes.
## What changed
- Add a nullable `name` column to persisted thread metadata and use it as the
canonical name for paginated threads.
- Route paginated name updates through the state database while retaining the
name index as best-effort compatibility data and preserving legacy thread
behavior.
- Return persisted names when reading, listing, searching, and resuming
paginated threads, and include them in state-database search matching.
## Testing
- Cover paginated name updates, reads, list/search results, and metadata-only
resume behavior, including stale or unavailable compatibility data.
GitOrigin-RevId: 5ac4dfa2a83682b43d59ecc87e0f515580164dca
