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 #4826.

Read the linked RFC and dependency #4826 first, then inspect how TypeSpec validation rules discover each service and how service.yaml is represented against its published JSON Schema. Done means every service has a schema-valid service.yaml whose version set matches the @versioned enum and the readme.md version set during coexistence.

Written by the indexing model from the issue text.