- Add OffsetSubscriber for managing offset-based subscriptions
- Implement OffsetSubscription with seeking, lag tracking, and range operations
- Add OffsetSeeker for offset validation and range utilities
- Create SMQOffsetIntegration for bridging offset management with SMQ broker
- Support all OffsetType variants: EXACT_OFFSET, RESET_TO_OFFSET, RESET_TO_EARLIEST, RESET_TO_LATEST
- Implement subscription lifecycle: create, seek, advance, close
- Add comprehensive offset validation and error handling
- Support batch record publishing and subscription
- Add offset metrics and partition information APIs
- Include extensive test coverage for all subscription scenarios:
- Basic subscription creation and record consumption
- Offset seeking and range operations
- Subscription lag tracking and end-of-stream detection
- Empty partition handling and error conditions
- Integration with offset assignment and high water marks
- All 40+ tests pass, providing robust offset-based messaging foundation
