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.

api/services/legacy_compat.py

@@ -11,12 +11,16 @@ from api.services.legacy_meter import identity_from_request, record_legacy_usage
 logger = logging.getLogger(__name__)
 
 _LEGACY_OWNER = "state-hub.api"
+# Planning horizon for legacy workstream interfaces; actual removal remains
+# legacy-meter-gated per docs/workplan-terminology-transition.md.
+_LEGACY_WORKSTREAM_SUNSET = "Wed, 30 Jun 2027 23:59:59 GMT"
 
 
 def mark_legacy_response(response: Response | None, replacement_ref: str) -> None:
     if response is None:
         return
     response.headers["Deprecation"] = "true"
+    response.headers["Sunset"] = _LEGACY_WORKSTREAM_SUNSET
     response.headers["X-StateHub-Replacement"] = replacement_ref
     response.headers.append("Link", f'<{replacement_ref}>; rel="successor-version"')
 
@@ -37,6 +41,37 @@ async def meter_legacy_query_param(
 ) -> None:
     interface_key = legacy_query_param_key(method, route, param)
     mark_legacy_response(response, replacement_ref)
+    try:
+        await record_legacy_usage(
+            session,
+            interface_key=interface_key,
+            interface_kind="rest_api",
+            replacement_ref=replacement_ref,
+            owner_component=_LEGACY_OWNER,
+            replacement_verified=True,
+            identity=identity_from_request(request),
+        )
+    except Exception:
+        await session.rollback()
+        logger.warning("legacy-meter failed to record %s", interface_key, exc_info=True)
+
+
+def legacy_body_field_key(method: str, route: str, field: str = "workstream_id") -> str:
+    return f"rest_api:{method} {route} {field}"
+
+
+async def meter_legacy_body_field(
+    *,
+    session: AsyncSession,
+    request: Request | None,
+    response: Response | None,
+    method: str,
+    route: str,
+    replacement_ref: str,
+    field: str = "workstream_id",
+) -> None:
+    interface_key = legacy_body_field_key(method, route, field)
+    mark_legacy_response(response, replacement_ref)
     try:
         await record_legacy_usage(
             session,