ci(schema): enforce locale-tag refs

[bokelley]

Summary

• add a high-recall JSON Schema lint that enforces canonical locale-tag references across string, array, union, conditional, wrapper-ref, and locale-keyed map shapes
• seed an exact, typed, self-cleaning disposition registry for legacy language boundaries and non-tag name collisions
• add focused regression coverage and run the guard in Build Check

Validation

• npm run test:language-tag-refs
• npm run test:schemas
• npm run precommit

Closes #6234