Finish STATE-WP-0069: retire legacy completion event and DELETE /workstreams

Stop dual-publishing org.statehub.workstream.completed; return 410 Gone for
legacy DELETE /workstreams/{id}. Migrate fix-consistency, MCP adhoc bootstrap,
and dashboard token summary to /workplans/. Add legacy-meter evidence capture
script and pytest snapshot; update docs and close out the workplan.

api/routers/workstreams.py

@@ -23,12 +23,8 @@ from api.schemas.workplan import (
     WorkplanUpdate,
 )
 from api.services.lifecycle import transition_workplan_status
-from api.services.legacy_compat import mark_legacy_response
-from api.services.legacy_meter import (
-    LegacyUsageIdentity,
-    identity_from_request,
-    record_legacy_usage,
-)
+from api.services.legacy_compat import legacy_response_headers, mark_legacy_response
+from api.services.legacy_meter import identity_from_request, record_legacy_usage
 from api.workplan_status import (
     is_supported_workplan_status,
     normalize_workplan_status,
@@ -47,7 +43,6 @@ _INDEX_REFRESH_TASK: asyncio.Task | None = None
 _INDEX_LAST_ERROR: str | None = None
 
 _LEGACY_OWNER = "state-hub.api"
-_COMPLETED_WORKSTREAM_EVENT = "org.statehub.workstream.completed"
 _COMPLETED_WORKPLAN_EVENT = "org.statehub.workplan.completed"
 
 
@@ -111,27 +106,6 @@ async def _meter_legacy_route(
         logger.warning("legacy-meter failed to record %s", interface_key, exc_info=True)
 
 
-async def _meter_legacy_event(
-    *,
-    session: AsyncSession,
-    subject: str,
-    replacement_ref: str,
-) -> None:
-    try:
-        await record_legacy_usage(
-            session,
-            interface_key=f"event_subject:{subject}",
-            interface_kind="event_subject",
-            replacement_ref=replacement_ref,
-            owner_component="state-hub.events",
-            replacement_verified=True,
-            identity=LegacyUsageIdentity(component_key="state-hub.events"),
-        )
-    except Exception:
-        await session.rollback()
-        logger.warning("legacy-meter failed to record event subject %s", subject, exc_info=True)
-
-
 async def _list_workplans(
     *,
     topic_id: uuid.UUID | None,
@@ -377,7 +351,6 @@ async def _publish_completion_events(wp: Workplan, session: AsyncSession) -> Non
         _COMPLETED_WORKPLAN_EVENT,
         attributes={
             "workplan_id": str(wp.id),
-            "legacy_workstream_id": str(wp.id),
             "slug": wp.slug,
             "title": wp.title,
             "topic_id": str(wp.topic_id) if wp.topic_id else None,
@@ -387,24 +360,6 @@ async def _publish_completion_events(wp: Workplan, session: AsyncSession) -> Non
     )
     asyncio.create_task(publish_event(_COMPLETED_WORKPLAN_EVENT, workplan_envelope))
 
-    await _meter_legacy_event(
-        session=session,
-        subject=_COMPLETED_WORKSTREAM_EVENT,
-        replacement_ref=_COMPLETED_WORKPLAN_EVENT,
-    )
-    legacy_envelope = EventEnvelope.new(
-        _COMPLETED_WORKSTREAM_EVENT,
-        attributes={
-            "workstream_id": str(wp.id),
-            "slug": wp.slug,
-            "title": wp.title,
-            "topic_id": str(wp.topic_id) if wp.topic_id else None,
-            "repo_id": str(wp.repo_id) if wp.repo_id else None,
-            "repo_goal_id": str(wp.repo_goal_id) if wp.repo_goal_id else None,
-        },
-    )
-    asyncio.create_task(publish_event(_COMPLETED_WORKSTREAM_EVENT, legacy_envelope))
-
 
 @router.get("/", response_model=list[WorkplanRead])
 async def list_workstreams(
@@ -581,21 +536,26 @@ async def update_workplan(
     return await _update_workplan(workplan_id=workplan_id, body=body, session=session)
 
 
-@router.delete("/{workstream_id}", response_model=WorkplanRead)
+@router.delete("/{workstream_id}", status_code=status.HTTP_410_GONE)
 async def archive_workstream(
     request: Request,
     response: Response,
     workstream_id: uuid.UUID,
     session: AsyncSession = Depends(get_session),
-) -> Workplan:
+) -> None:
+    replacement_ref = "DELETE /workplans/{workplan_id}"
     await _meter_legacy_route(
         session=session,
         request=request,
         response=response,
         interface_key=_legacy_key("DELETE", "/workstreams/{workstream_id}"),
-        replacement_ref="/workplans/{workplan_id}",
+        replacement_ref=replacement_ref,
+    )
+    raise HTTPException(
+        status_code=status.HTTP_410_GONE,
+        detail="Legacy DELETE /workstreams/{workstream_id} retired; use DELETE /workplans/{workplan_id}",
+        headers=legacy_response_headers(replacement_ref),
     )
-    return await _archive_workplan(workplan_id=workstream_id, session=session)
 
 
 @workplan_router.delete("/{workplan_id}", response_model=WorkplanRead)