docs: update README for v1.4 (OATR integration, commitments, new exam…

…ple)

- Badge updated from v1.3 to v1.4
- Quick start example updated to v1.4
- Integration tiers table: Tier 3 now mentions oatr_issuer_id,
  new Tier 3+ row for commitments
- Examples table: added v14-consolidated-trust.json
- Specification summary: added commitments to optional fields

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

1.3.0

1.2.1