RFC #661: glossary maintenance & governance cadence

## Context

Open question from RFC #661 (Spectrum Design System Glossary), tracked in `docs/rfc-coordination.md`.

Phases 0–2 are complete and the three-registry boundary is formalized. Define: who owns additions to `anatomy-terms.json`, `token-objects.json`, and `categories.json`; the review/approval process for new entries; and how often the registry is audited against component declarations.

## References
- RFC #661: https://github.com/adobe/spectrum-design-data/discussions/661
- `docs/rfc-coordination.md` RFC #661 row
- `packages/design-data-spec/registry/`

Start with the RFC #661 row in docs/rfc-coordination.md and the discussion linked in the issue, then inspect packages/design-data-spec/registry/. Done means documenting ownership for anatomy-terms.json, token-objects.json, and categories.json, along with the entry review process and registry audit cadence.

Written by the indexing model from the issue text.