fix(coroner): playbook-kind postmortems stop rendering dead buttons

A kind=playbook process change drafts into the playbook queue at propose
time and both approve/reject refuse it - but legacy rows carry no marker
status, so the response defaulted to proposed and the panel rendered
approve/dismiss buttons that bounce forever. The list route now derives
not_applicable for playbook-kind changes regardless of stored status,
which the panel already renders as its Drafted-as-playbook badge.

roboco/api/routes/coroner.py

@@ -25,7 +25,7 @@ from roboco.api.schemas.coroner import (
 )
 from roboco.foundation.policy.content import markers
 from roboco.security import guard_deco
-from roboco.services.coroner_service import get_coroner_service
+from roboco.services.coroner_service import PLAYBOOK_KIND, get_coroner_service
 from roboco.services.task import get_task_service
 
 if TYPE_CHECKING:
@@ -55,7 +55,16 @@ def _to_response(task: TaskTable) -> PostmortemResponse:
         process_change_kind=process_change.get("kind"),
         process_change_description=process_change.get("description"),
         playbook_id=postmortem.get("playbook_id"),
-        process_change_status=process_change.get("status", "proposed"),
+        # A playbook-kind change already drafted into the playbook queue at
+        # propose time — there is nothing to decide, but the stored status
+        # stays "proposed", which left the panel rendering approve/dismiss
+        # buttons that both verbs refuse forever. Derive the terminal status
+        # the panel's contract expects instead.
+        process_change_status=(
+            "not_applicable"
+            if process_change.get("kind") == PLAYBOOK_KIND
+            else process_change.get("status", "proposed")
+        ),
         process_change_reject_reason=process_change.get("reject_reason"),
         process_change_materialized_task_id=process_change.get("materialized_task_id"),
     )

roboco/services/coroner_service.py

@@ -53,7 +53,7 @@ if TYPE_CHECKING:
 
     from roboco.db.tables import TaskTable
 
-_PLAYBOOK_KIND = "playbook"
+PLAYBOOK_KIND = "playbook"
 
 
 @dataclass(frozen=True)
@@ -90,7 +90,7 @@ class CoronerService(BaseService):
         task, payload, process_change = await self._find(task_id)
         if task is None or payload is None or process_change is None:
             return None
-        if process_change["kind"] == _PLAYBOOK_KIND:
+        if process_change["kind"] == PLAYBOOK_KIND:
             return self._playbook_result()
         if process_change["status"] == "approved":
             return ProcessChangeResult(
@@ -139,7 +139,7 @@ class CoronerService(BaseService):
         task, payload, process_change = await self._find(task_id)
         if task is None or payload is None or process_change is None:
             return None
-        if process_change["kind"] == _PLAYBOOK_KIND:
+        if process_change["kind"] == PLAYBOOK_KIND:
             return self._playbook_result()
         if process_change["status"] == "rejected":
             return ProcessChangeResult(

tests/integration/test_coroner_routes.py

@@ -200,6 +200,28 @@ async def test_list_postmortems_returns_completed_autopsy(
     assert row["failed_stage"] == "awaiting_qa"
 
 
+@pytest.mark.asyncio
+async def test_list_postmortems_derives_not_applicable_for_playbook_kind(
+    db_session: AsyncSession, ceo_client: AsyncClient
+) -> None:
+    """A playbook-kind process change reads as not_applicable even when the
+    stored marker has NO status key — legacy rows predate the propose-time
+    stamp, and the raw default ("proposed") left the panel rendering
+    approve/dismiss buttons both verbs refuse forever."""
+    task = await _seed_completed_postmortem(db_session)
+    payload = markers.get_coroner_postmortem(task)
+    assert payload is not None
+    payload["process_change"] = {
+        "kind": "playbook",
+        "description": "run the named command end-to-end",
+    }
+    markers.set_coroner_postmortem(task, payload)
+    await db_session.flush()
+    resp = await ceo_client.get("/api/coroner/postmortems")
+    assert resp.status_code == HTTPStatus.OK
+    assert resp.json()[0]["process_change_status"] == "not_applicable"
+
+
 @pytest.mark.asyncio
 async def test_list_postmortems_forbidden_for_non_ceo(
     dev_client: AsyncClient,