Idempotent IDs not generated for annotations or batch publish (RSAN1c4, RSC22d)

[paddybyers]

Spec points

• RSAN1c4: "If `idempotentRestPublishing` is enabled and the annotation has an empty `id`, the SDK should generate a base64-encoded random string, append `:0`, and set it as the `Annotation.id`."
• RSC22d: "If `idempotentRestPublishing` is enabled, then RSL1k1 should be applied (to each `BatchPublishSpec` separately)."

Observed behaviour

Only `RestChannel.publish()` generates idempotent IDs (via the `allEmptyIds()` / `idempotentRestPublishing` code path). Neither `RestAnnotations.publish()` nor `batchPublish()` generates them — messages are sent exactly as provided by the caller, with no `id` fields added.

Failing tests (2)

Test	Expected	Actual
`RSAN1c4 - idempotent ID generated`	Annotation `id` matches `:0` pattern	`id` is undefined
`RSC22d - batch publish generates idempotent IDs`	Messages in batch have generated `id` fields	`id` property absent

Reproduction

```bash
RUN_DEVIATIONS=1 npx mocha --grep "RSAN1c4" test/uts/rest/channel/annotations.test.ts
RUN_DEVIATIONS=1 npx mocha --grep "RSC22d" test/uts/rest/batch_publish.test.ts
```

From PR #2191, branch `uts-rest`.

┆Issue is synchronized with this Jira Task by Unito