Wire the PatchUpdated events through app_server (#18289)

Wires patch_updated events through app_server. These events are parsed
and streamed while apply_patch is being written by the model. Also adds 500ms of buffering to the patch_updated events in the diff_consumer.

The eventual goal is to use this to display better progress indicators in
the codex app.

codex-rs/app-server/src/bespoke_event_handling.rs

@@ -40,6 +40,7 @@ use codex_app_server_protocol::ExecCommandApprovalResponse;
 use codex_app_server_protocol::ExecPolicyAmendment as V2ExecPolicyAmendment;
 use codex_app_server_protocol::FileChangeApprovalDecision;
 use codex_app_server_protocol::FileChangeOutputDeltaNotification;
+use codex_app_server_protocol::FileChangePatchUpdatedNotification;
 use codex_app_server_protocol::FileChangeRequestApprovalParams;
 use codex_app_server_protocol::FileChangeRequestApprovalResponse;
 use codex_app_server_protocol::FileUpdateChange;
@@ -1636,6 +1637,17 @@ pub(crate) async fn apply_bespoke_event_handling(
                     .await;
             }
         }
+        EventMsg::PatchApplyUpdated(event) => {
+            let notification = FileChangePatchUpdatedNotification {
+                thread_id: conversation_id.to_string(),
+                turn_id: event_turn_id.clone(),
+                item_id: event.call_id,
+                changes: convert_patch_changes(&event.changes),
+            };
+            outgoing
+                .send_server_notification(ServerNotification::FileChangePatchUpdated(notification))
+                .await;
+        }
         EventMsg::PatchApplyEnd(patch_end_event) => {
             // Until we migrate the core to be aware of a first class FileChangeItem
             // and emit the corresponding EventMsg, we repurpose the call_id as the item_id.