test(gateway): drop the helper-level recursion-cap FIFO case

The runner-level depth-cap tests drive the same drain/promote/requeue
sequence through the real recursion, so the helper copy adds no coverage.

tests/gateway/test_queue_consumption.py

@@ -168,54 +168,6 @@ class TestQueueConsumptionAfterCompletion:
         # gets the next-in-line item.
         assert adapter._pending_messages[session_key].text == "Q2"
 
-    def test_recursion_cap_requeue_preserves_staged_fifo_head(self):
-        """Requeueing the current item must not overwrite the promoted next item."""
-        from gateway.run import GatewayRunner
-
-        runner = GatewayRunner.__new__(GatewayRunner)
-        runner._queued_events = {}
-        adapter = _StubAdapter()
-        session_key = "discord:thread:coffee"
-
-        for text in ("Q1", "Q2", "Q3"):
-            runner._enqueue_fifo(
-                session_key,
-                MessageEvent(
-                    text=text,
-                    message_type=MessageType.TEXT,
-                    source=MagicMock(),
-                    message_id=f"q-{text}",
-                ),
-                adapter,
-            )
-
-        # Drain Q1 and promote Q2 into the slot; Q3 remains in overflow.
-        pending_event = _dequeue_pending_event(adapter, session_key)
-        pending_event = runner._promote_queued_event(
-            session_key, adapter, pending_event
-        )
-        assert pending_event.text == "Q1"
-        assert adapter._pending_messages[session_key].text == "Q2"
-        assert [event.text for event in runner._queued_events[session_key]] == [
-            "Q3"
-        ]
-
-        # The recursion cap restores Q1 without losing or reordering Q2/Q3.
-        runner._requeue_event_at_front(session_key, pending_event, adapter)
-        assert adapter._pending_messages[session_key].text == "Q1"
-        assert [event.text for event in runner._queued_events[session_key]] == [
-            "Q2",
-            "Q3",
-        ]
-
-        drained = []
-        for _ in range(3):
-            event = _dequeue_pending_event(adapter, session_key)
-            event = runner._promote_queued_event(session_key, adapter, event)
-            drained.append(event.text)
-        assert drained == ["Q1", "Q2", "Q3"]
-        assert runner._queue_depth(session_key, adapter=adapter) == 0
-
 
 class TestBusyInputModeQueueFifo:
     """Regression coverage for issue #28503.