Pass 1 on PATH integration

app/services/dm_ack_apply.py

@@ -0,0 +1,26 @@
+"""Shared direct-message ACK application logic."""
+
+from collections.abc import Callable
+from typing import Any
+
+from app.services import dm_ack_tracker
+from app.services.messages import increment_ack_and_broadcast
+
+BroadcastFn = Callable[..., Any]
+
+
+async def apply_dm_ack_code(ack_code: str, *, broadcast_fn: BroadcastFn) -> bool:
+    """Apply a DM ACK code using the shared pending/buffered state machine.
+
+    Returns True when the ACK matched a pending message, False when it was buffered.
+    """
+    dm_ack_tracker.cleanup_expired_acks()
+
+    message_id = dm_ack_tracker.pop_pending_ack(ack_code)
+    if message_id is None:
+        dm_ack_tracker.buffer_unmatched_ack(ack_code)
+        return False
+
+    dm_ack_tracker.clear_pending_acks_for_message(message_id)
+    await increment_ack_and_broadcast(message_id=message_id, broadcast_fn=broadcast_fn)
+    return True