chore: rename ATgora to Barazo
Rename brand from ATgora to Barazo across all code, schemas, and docs.
Key changes:
- Lexicon namespace: forum.atgora.* -> forum.barazo.*
- npm scope: @atgora-forum -> @barazo-forum
- All schema IDs, cross-references, and generated types updated
- Validation, tests, README, and CI config updated
Part of org-wide rename. See brand/naming-decision-barazo.md for rationale.