fix(api): require substantive audit notes on human task-decision endpoints

Audit/tracing rule: every human decision must record its rationale. These
panel-facing routes accepted empty/absent notes, leaving no trail:
- docs-complete: now requires notes (>=20) — what was documented
- submit-pm-review: now requires notes (>=20) — what is ready for review
- complete: now requires justification (>=20) — why the task is done

Mirrors the existing pass-qa / ceo-approve notes gates (checked after the
404/403 so not-found and forbidden still take precedence). submit-qa is
left as-is: it already gates on commits + PR + progress_updates +
self_verified, and the panel collects no extra note there to drop.
Tests updated to send notes; added complete-without-justification reject.

roboco/api/routes/tasks.py

@@ -1084,11 +1084,19 @@ async def docs_complete(
 
     Transitions task from awaiting_documentation to awaiting_pm_review.
     """
+    # Audit: the documenter must record what was documented, so the next
+    # reader knows what exists. No note → empty trail, so reject.
+    if not data or not data.notes or len(data.notes.strip()) < _MIN_NOTES_CHARS:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=(
+                "DOC_NOTES_REQUIRED: docs-complete must include notes (>=20 "
+                "chars) describing what was documented and where."
+            ),
+        )
     service = get_task_service(db)
     try:
-        task = await service.docs_complete_for_task(
-            task_id, agent, notes=(data.notes if data else None)
-        )
+        task = await service.docs_complete_for_task(task_id, agent, notes=data.notes)
     except ServiceError as e:
         raise _translate_error(e) from e
     return task_to_response(task)
@@ -1122,7 +1130,17 @@ async def submit_for_pm_review(
             detail="Only the assigned agent can submit for PM review",
         )
 
-    notes = data.notes if data else None
+    # Audit: the submitter must record what is ready for review.
+    if not data or not data.notes or len(data.notes.strip()) < _MIN_NOTES_CHARS:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=(
+                "PM_REVIEW_NOTES_REQUIRED: submit-pm-review must include notes "
+                "(>=20 chars) summarizing what is ready for the PM to review."
+            ),
+        )
+
+    notes = data.notes
     task = await service.submit_for_pm_review(task_id, agent.role.value, notes)
     if not task:
         raise HTTPException(
@@ -1159,6 +1177,16 @@ async def complete_task(
     If force_with_cancelled=True, PM can complete despite cancelled subtasks.
     Requires justification. Does NOT apply to pending/in_progress subtasks.
     """
+    # Audit: completing a task is a decision that must carry its rationale.
+    justification = data.justification if data else None
+    if not justification or len(justification.strip()) < _MIN_NOTES_CHARS:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=(
+                "COMPLETE_JUSTIFICATION_REQUIRED: complete must include a "
+                "justification (>=20 chars) recording why the task is done."
+            ),
+        )
     service = get_task_service(db)
     try:
         task = await service.complete_task_for_agent(
@@ -1166,7 +1194,7 @@ async def complete_task(
             agent,
             permissions,
             force_with_cancelled=(data.force_with_cancelled if data else False),
-            justification=(data.justification if data else None),
+            justification=justification,
         )
     except ServiceError as e:
         raise _translate_error(e) from e

tests/integration/test_tasks_routes.py

@@ -2209,6 +2209,7 @@ async def test_submit_pm_review_service_returns_none(task_client: dict) -> None:
         mock_factory.return_value = instance
         response = await task_client["client"].post(
             f"/api/tasks/{task.id}/submit-pm-review",
+            json={"notes": "Ready for PM review — all criteria met."},
             headers=_HDR,
         )
     assert response.status_code == HTTPStatus.BAD_REQUEST
@@ -2230,12 +2231,29 @@ async def test_complete_task_success(task_client: dict) -> None:
         mock_factory.return_value = instance
         response = await task_client["client"].post(
             f"/api/tasks/{task.id}/complete",
-            json={"force_with_cancelled": False},
+            json={
+                "force_with_cancelled": False,
+                "justification": "All acceptance criteria met; merging.",
+            },
             headers=_HDR,
         )
     assert response.status_code == HTTPStatus.OK
 
 
+@pytest.mark.asyncio
+async def test_complete_without_justification_rejected(task_client: dict) -> None:
+    """Audit: completing a task must carry its rationale (>= 20 chars)."""
+    task = _seed_task(task_client)
+    await task_client["db"].flush()
+    response = await task_client["client"].post(
+        f"/api/tasks/{task.id}/complete",
+        json={"force_with_cancelled": False},
+        headers=_HDR,
+    )
+    assert response.status_code == HTTPStatus.BAD_REQUEST
+    assert "JUSTIFICATION_REQUIRED" in response.json()["detail"]
+
+
 # ---------------------------------------------------------------------------
 # cancel: service returns None branch (1162-1167)
 # ---------------------------------------------------------------------------