Code review improvements to internal/config/sync.go:
1. Warning suppression toggle
- Add ConfigWarnings bool to enable/disable warnings
- Add ConfigWarningWriter io.Writer for testable output
2. Consolidate sync mode constants
- cmd/bd/sync_mode.go now imports from internal/config
- Single source of truth for mode values
- Uses shared IsValidSyncMode() for validation
3. Fix empty sovereignty semantics
- Empty now returns SovereigntyNone (no restriction)
- Only non-empty invalid values fall back to T1 with warning
4. Export validation helpers
- IsValidSyncMode(), IsValidConflictStrategy(), IsValidSovereignty()
- ValidSyncModes(), ValidConflictStrategies(), ValidSovereigntyTiers()
- String() methods on all typed values
5. Logger interface
- ConfigWarningWriter allows custom logging destinations
- Tests can capture warnings without os.Stderr manipulation
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
521239cfdc