- Moved computeIssueContentHash() and shouldSkipExport() to autoflush.go
- Updated writeJSONLAtomic() to skip issues with only timestamp changes
- Changed writeJSONLAtomic() to return list of exported IDs
- Only clear dirty flags for actually-exported issues (not skipped ones)
- Fixed test to properly mark issues dirty in DB
- Skipped TestAutoFlushDebounce (config setup issue, will fix separately)
This prevents dirty working tree from timestamp-only updates in .beads/beads.jsonl