Epic: service.yaml rollout

**Epic** tracking the rollout of **`service.yaml`** in `Azure/typespec-azure` — a machine-readable per-service version-metadata file that replaces the version-metadata role of `readme.md`.

RFC: https://github.com/Azure/azure-rest-api-specs/blob/rfc/unified-examples-format/documentation/rfc/service-yaml.md

`service.yaml` declares the ordered list of API versions for a service (with `swagger-files` for legacy swagger versions). It becomes the source of version ordering that the [Unified Examples Format](https://github.com/Azure/azure-rest-api-specs/blob/rfc/unified-examples-format/documentation/rfc/unified-examples-format.md) `since`-resolution depends on.

### Rollout
- [ ] #4826 — `service.yaml` schema + conversion tool + repo-wide migration
- [ ] #4827 — `typespec-autorest`: inject API versions from TypeSpec
- [ ] #4828 — TSV validation: require + sync-check `service.yaml`
- [ ] #4829 — Contributor docs: author API versions via `service.yaml`
- [ ] #4830 — Remove `readme.md`

_Child issues are attached as sub-issues below._

Start with documentation/rfc/service-yaml.md, then review child issues #4826–#4830 to understand the rollout boundaries. The epic is done when the schema, conversion and validation work, TypeSpec version injection, contributor documentation, and readme.md removal are completed and all listed sub-issues are closed.

Written by the indexing model from the issue text.