test(memhub): register the sedimentation switch test in the core test inventory

New core test files must appear in TEST_INDEX.md and in the classification
inventory's expected count and digest, and the backfill case needs a settled
turn because an unanswered user tail is not backfill material.

memhub/apps/core/tests/TEST_INDEX.md

@@ -328,6 +328,7 @@
 | `test_secret_store_error_codes.py` | `integration` | 3925a kernel item 3: keychain failure classification and backoff that heals. |
 | `test_secure_storage.py` | `integration` | 覆盖 isolated keychain service namespace、custom keychain service is refused outside isolated tests、packaged keychain budget covers loaded process startup 等 20 个场景。 |
 | `test_sedimentation_concurrency.py` | `contract` | Sedimentation runs several harnesses at once, but one harness at a time. |
+| `test_sedimentation_switch.py` | `contract` | Stopping model-driven sedimentation without losing the configuration. |
 | `test_service_level_pressure_acceptance.py` | `contract` | 覆盖 workbuddy recall remains available during 100k import 场景。 |
 | `test_service_levels.py` | `contract` | 覆盖 background never consumes the realtime reservation、realtime is next for the same source after background yields、import history gets one slice after nine realtime admissions 等 8 个场景。 |
 | `test_session_inbox.py` | `contract` | A session inbox is not a shared mailbox and a pull is not adoption. |
@@ -386,4 +387,4 @@
 | `test_workspace_recall.py` | `contract` | Workspace memories were unreachable from every host; these pin the way in. |
 | `test_write_queue_lease_renewal.py` | `contract` | Rule 8: a lease must outlive the work it covers, and be renewed while it runs. |
 
-共 381 个测试文件。
+共 382 个测试文件。

memhub/apps/core/tests/core_test_classification.py

@@ -14,8 +14,8 @@ from pathlib import Path
 import pytest
 
 PRIMARY_MARKERS = ("unit", "contract", "integration", "performance", "live")
-EXPECTED_TEST_FILE_COUNT = 381
-EXPECTED_TEST_FILES_SHA256 = "1f5100ccee78a9a4ea91805ec07b2054ee4a18911a8162943acedf471ae9b3e7"
+EXPECTED_TEST_FILE_COUNT = 382
+EXPECTED_TEST_FILES_SHA256 = "f08fbe22bc3af3df5c340ec75b94ba42287220bb728b34cbeadd5f5c93eea40b"
 
 # Pure transformations, validation models, parity checks and state machines.
 # This list is intentionally small: uncertain files default to contract.

memhub/apps/core/tests/test_sedimentation_switch.py

@@ -145,7 +145,28 @@ def test_stopped_switch_enqueues_nothing(tmp_path) -> None:
 def test_stopped_switch_prepares_no_backfill(tmp_path) -> None:
     flag = _Flag(False)
     evidence, tasks, active, supervisor, _profiles, _secrets = _stores(tmp_path, flag)
-    _task(evidence, tasks, active, index=1)
+    # No task is queued yet: backfill is what would create one for this
+    # conversation, so the stopped switch must keep it from creating any.
+    # A settled turn (question plus answer): an unanswered user tail is not
+    # backfill material, so the conversation needs both records.
+    for message_id, role, written_by, verbatim in (
+        ("m-old", "user", WrittenBy.PERSON, "Remember this too."),
+        ("m-old-reply", "assistant", WrittenBy.AGENT, "Saved."),
+    ):
+        evidence.put(
+            EvidenceInput(
+                source_id="cursor",
+                workspace="/Users/me/project",
+                conversation_id="conv-old",
+                message_id=message_id,
+                correlation_id=message_id,
+                role=role,
+                written_by=written_by,
+                created_at=NOW - timedelta(days=1),
+                verbatim=verbatim,
+                origin_meta={EvidenceOrigin.FILE: OriginMetadata()},
+            )
+        )
 
     assert supervisor.prepare_backfill() == []