- Add federation.config.ts with UUID v4 validation for DEFAULT_WORKSPACE_ID
- Validate at module initialization (fail fast if misconfigured)
- Replace hardcoded "default" fallback with proper validation
- Add 18 tests covering valid UUIDs, invalid formats, and missing values
- Clear error messages with expected UUID format
Refs #338
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
