STATE-WP-0069 T04: Sunset headers and POST /progress body metering

Add Sunset to legacy compat responses (Jun 2027 planning horizon).
Meter POST /progress/ bodies that use workstream_id; wire hub-core body
hook. Consolidate workstreams deprecation headers via legacy_compat.

docs/workplan-terminology-legacy-retirement-backlog.md

@@ -75,6 +75,7 @@ These accept `workstream_id` alongside `workplan_id` on preferred routes:
 | `rest_api:GET /token-events/?workstream_id` | `GET /token-events/` | `GET /token-events/?workplan_id=` |
 | `rest_api:GET /execution/launch-requests?workstream_id` | `GET /execution/launch-requests` | `GET /execution/launch-requests?workplan_id=` |
 | `rest_api:GET /progress/?workstream_id` | `GET /progress/` | `GET /progress/?workplan_id=` |
+| `rest_api:POST /progress/ workstream_id` | `POST /progress/` | `POST /progress/` with `workplan_id` body field |
 
 Retire param aliases in T04 after zero-usage windows; callers surface via
 `X-StateHub-Component` in weekly review.

docs/workplan-terminology-transition.md

@@ -39,6 +39,7 @@ Physical database renames are intentionally out of scope for this workplan.
 Legacy REST responses include:
 
 - `Deprecation: true`
+- `Sunset: Wed, 30 Jun 2027 23:59:59 GMT` (planning horizon; removal remains legacy-meter-gated)
 - `X-StateHub-Replacement: <preferred interface>`
 - `Link: <<preferred interface>>; rel="successor-version"`