## Summary
When metadata.json gets deleted (git clean, merge conflict, rebase), the
version tracking code auto-recreates it using DefaultConfig() which hardcoded
jsonl_export to 'issues.jsonl'. But many repos (including beads itself) use
'beads.jsonl', causing a mismatch between config and actual JSONL file.
## Changes
1. **bd doctor --fix auto-detection** (cmd/bd/doctor/fix/database_config.go)
- New DatabaseConfig() fix function that auto-detects actual JSONL file
- Prefers beads.jsonl over issues.jsonl (canonical name)
- Skips backup files and merge artifacts
- Wired into doctor.go applyFixes()
2. **Version tracking auto-detection** (cmd/bd/version_tracking.go)
- trackBdVersion() now scans for existing JSONL files before defaulting
- Prevents mismatches when metadata.json gets recreated
- Added findActualJSONLFile() helper function
3. **Canonical default name** (internal/configfile/configfile.go)
- DefaultConfig() changed from issues.jsonl to beads.jsonl
- Aligns with canonical naming convention
4. **FindJSONLPath preference** (internal/beads/beads.go)
- Now prefers beads.jsonl over issues.jsonl when scanning
- Default changed from issues.jsonl to beads.jsonl
5. **Test coverage**
- Added comprehensive tests for DatabaseConfig fix
- Updated configfile tests for new default
- Verified backup file skipping logic
## Testing
- All existing tests pass
- New tests verify auto-fix behavior
- Integration tested with simulated mismatches
Closes: bd-afd
d1641c7d2e