test(chats): ensure saved chat delete clears history only

docs/core-checklist-status.md

@@ -11,7 +11,7 @@ Legend:
 2. User Profile - `DONE` (username, name, avatar, bio, update)
 3. User Status - `PARTIAL` (online/last seen/offline; "recently" heuristic limited)
 4. Contacts - `PARTIAL` (list/search/add/remove/block/unblock; `add by email` flow covered by integration tests including `success/not found/blocked conflict`; UX moved to menu)
-5. Chat List - `DONE` (all/pinned/archive/sort/unread)
+5. Chat List - `DONE` (all/pinned/archive/sort/unread; saved-messages delete behavior covered: clear history without deleting chat)
 6. Chat Types - `DONE` (private/group/channel)
 7. Chat Creation - `DONE` (private/group/channel)
 8. Messages (base) - `DONE` (send/read/edit/delete/delete for all; 7-day edit window enforced and covered by integration tests; group UI shows sender names over bubbles + sender avatars on incoming message clusters)

tests/test_chat_message_flow.py

@@ -101,6 +101,40 @@ async def test_edit_message_older_than_7_days_is_forbidden(client, db_session):
     assert "7 days" in edit_message_response.json().get("detail", "")
 
 
+async def test_delete_saved_messages_chat_clears_messages_but_keeps_chat(client, db_session):
+    user = await _create_verified_user(
+        client,
+        db_session,
+        "saved_clear_user@example.com",
+        "saved_clear_user",
+        "strongpass123",
+    )
+    auth = {"Authorization": f"Bearer {user['access_token']}"}
+
+    saved_chat_response = await client.get("/api/v1/chats/saved", headers=auth)
+    assert saved_chat_response.status_code == 200
+    saved_chat = saved_chat_response.json()
+    saved_chat_id = saved_chat["id"]
+
+    send_message_response = await client.post(
+        "/api/v1/messages",
+        headers=auth,
+        json={"chat_id": saved_chat_id, "type": "text", "text": "saved note"},
+    )
+    assert send_message_response.status_code == 201
+
+    delete_chat_response = await client.delete(f"/api/v1/chats/{saved_chat_id}", headers=auth)
+    assert delete_chat_response.status_code == 204
+
+    saved_chat_after_delete = await client.get("/api/v1/chats/saved", headers=auth)
+    assert saved_chat_after_delete.status_code == 200
+    assert saved_chat_after_delete.json()["id"] == saved_chat_id
+
+    messages_after_delete = await client.get(f"/api/v1/messages/{saved_chat_id}", headers=auth)
+    assert messages_after_delete.status_code == 200
+    assert messages_after_delete.json() == []
+
+
 async def test_private_chat_respects_contacts_only_policy(client, db_session):
     u1 = await _create_verified_user(client, db_session, "pm_u1@example.com", "pm_user_one", "strongpass123")
     u2 = await _create_verified_user(client, db_session, "pm_u2@example.com", "pm_user_two", "strongpass123")