This change fixes the issue where 'bd sync' would fail with a false-positive
"JSONL is newer than database" error after the daemon auto-exports.
Root Cause:
- Daemon exports local changes to JSONL, updating its timestamp
- bd sync sees JSONL.mtime > DB.mtime and incorrectly assumes external changes
- This blocks export even though content is identical
Solution:
- Modified isJSONLNewer() to use SHA256 content hash comparison
- Only triggers auto-import when JSONL is newer AND content differs
- Prevents false positives from daemon auto-export timestamp updates
- Maintains conservative fallback if hashes can't be computed
Changes:
- Added computeJSONLHash() and computeDBHash() helper functions
- Created isJSONLNewerWithStore() to support testing with explicit store
- Added comprehensive tests for content-based comparison logic
- All existing tests pass, including export_mtime tests
Fixes: bd-lm2q
d0e70473cc