- Rename batchJob.status → .state; update all references
- Add done chan struct{} to batchJob, closed on terminal state
- Add statewait file to b/<id>/: blocks until state leaves "running"
- Add CurrentWaitValue/Wait methods to BatchJobStore
- Extend Topen handler to snapshot waitBase for b/ wait files
- Extend Tread handler for b/ to serve statewait with 5s timeout/retry
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>