B3 — TSV validation: require + sync-check service.yaml

Part of #4825. RFC: https://github.com/Azure/azure-rest-api-specs/blob/rfc/unified-examples-format/documentation/rfc/service-yaml.md Add a **TypeSpec validation (TSV)** rule for `service.yaml`: - **present** for every service - **schema-valid** against the published JSON Schema - **in sync** — the version set matches the `@versioned` enum (TypeSpec) and the `readme.md` version set during coexistence Depends on B1.