The generated schema currently advertises a GitHub blob page as its $id,
which returns HTML rather than the schema document itself.
This updates the source-of-truth generator and checked-in schema to use
a JSON-serving raw URL, and adds a regression assertion for the canonical
metadata value.
Constraint: Must keep the checked-in schema aligned with the generator output
Rejected: Leave the blob URL in place | Schema consumers dereferencing $id receive HTML
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: If the schema is moved in the future, keep $id pointing at a JSON-serving canonical URL
Tested: pnpm --dir packages/types exec vitest run src/__tests__/roomodes-schema.spec.ts src/__tests__/roomodes-schema-sync.spec.ts
Not-tested: External IDE/schema consumer end-to-end dereference behavior
