RFC #661: glossary prioritization of new collections

## Context

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

Beyond the current three registries (anatomy-terms, token-objects, categories), identify which new collections provide the most value next — e.g. a motion/animation terms registry, a color semantic terms registry, or a platform-adapter vocabulary. Prioritize based on which SPEC rules or authoring tooling most needs the additional vocabulary.

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

Start with the RFC #661 discussion and the RFC #661 row in docs/rfc-coordination.md. Compare the proposed motion/animation, color semantic, and platform-adapter collections against the SPEC rules and authoring tooling needs described there. Done means documenting a justified priority order for the next collections.

Written by the indexing model from the issue text.