release 0.3.0

## Bump
- [ ] Major
- [x] Minor
- [ ] Patch
- [ ] Skip

## Changelog

### Added
- Explicit validation record typing in DataQualityValidationRecord using `validationType` (`single_violation` and `group_violation`) and grouped subtype handling via `groupViolationType` (`global_overflow`, `value_overflow`, `pass`).
- Grouped PASS heartbeat behavior for all-green uniqueness runs.

### Changed
- Uniqueness overflow behavior to deterministic N+1 mode detection (`aggregate` and `instances.list` with 101 semantics), including global-overflow shortcut and per-value overflow grouping.
- Documentation and records contract guidance to support deterministic consumer branching for grouped vs single violation flows.

### Improved
- Release packaging and communication alignment for the 0.3.0 contract change context from issue #217.
