## Why
Paginated threads allow only one app-server process to write at a time. Archive and delete operations must not mutate a thread or its spawned descendants while another process owns any of them.
## What changed
- Acquire paginated writer locks for the full archive or deletion set before changing rollout files, including descendants whose rollout has not materialized yet.
- Add a batch archive store operation so ownership conflicts are detected before any thread in the subtree is archived.
- Return ownership conflicts as JSON-RPC invalid-request errors and document the behavior.
## Testing
- Cover archive and deletion conflicts for owned threads and descendants, including unmaterialized rollouts.
- Verify deletion still removes rollouts with unreadable metadata.
GitOrigin-RevId: f62a3e0c1ee2631cea48dd9145b588a1486e2425
Owen Lin
963316583b