## Why
Cold rollout files can still have active writers. Compression must not replace their files while writes are pending, including background work that outlives the local thread store.
## What changed
- Share cross-process writer locks between the rollout compressor and local thread store. Skip busy threads and recheck file state under coordination before publishing compressed files.
- Retain writer ownership through recorder background I/O and compressed rollout materialization. Wait for writers to exit on shutdown or discard, and stop queued file work before deletion.
- Route rollout metadata patches through owned recorders, reject competing writers before updating SQLite, and serialize metadata appends with shutdown.
## Testing
Add regression coverage for compression with live and detached writers, parallel cold-file compression, publication locking, metadata ownership conflicts, updates to compressed rollouts, concurrent shutdown, and discarding deferred items.
GitOrigin-RevId: c52f4037eb2019e8095b554e29bf531af95aa4bd
jif
73a1148c9c