Reduce response serialization and rollout scan overhead (#36006)

## What changed

- Keep `ClientResponsePayload` typed through the app-server outgoing queue and serialize it at the transport boundary, avoiding an intermediate `serde_json::Value` while preserving the JSON-RPC wire shape.
- Return a JSON-RPC internal error when a response cannot be serialized, including over remote control, and skip unserializable analytics responses.
- Scan reverse JSONL input a chunk at a time with a larger buffer instead of processing each byte individually.

## Testing

- Cover typed response serialization and serialization failures for direct and remote-control transports.
- Cover filtering unserializable responses from analytics.

GitOrigin-RevId: cc4fd7a43461a273315bb95261bd1ae3ff65fbf7

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

@@ -641,7 +641,10 @@ async fn start_uninitialized(args: InProcessStartArgs) -> IoResult<InProcessClie
                     match outgoing_message {
                         OutgoingMessage::Response(response) => {
                             if let Some(response_tx) = pending_request_responses.remove(&response.id) {
-                                let _ = response_tx.send(Ok(response.result));
+                                let result = serde_json::to_value(response.result).map_err(|err| {
+                                    internal_error(format!("failed to serialize response: {err}"))
+                                });
+                                let _ = response_tx.send(result);
                             } else {
                                 warn!(
                                     request_id = ?response.id,