refactor(acp-nats): replace fallback byte literal with expect in error_response_bytes

Response::Error only contains integers, strings, and Option — serde_json
serialization is infallible for this type. Replace the dead-code
unwrap_or_else fallback string with an expect so the invariant is
explicit and the raw JSON byte literal is gone.

Signed-off-by: Yordis Prieto <yordis.prieto@gmail.com>

Author: yordis

rsworkspace/crates/acp-nats/src/client/mod.rs

@@ -17,8 +17,9 @@ use trogon_std::time::GetElapsed;
 
 fn error_response_bytes(id: RequestId, error: Error) -> Bytes {
     let msg = JsonRpcMessage::wrap(Response::<()>::Error { id, error });
+    // Response<()>::Error only contains integers, strings, and Option — serialization is infallible.
     serde_json::to_vec(&msg)
-        .unwrap_or_else(|_| br#"{"jsonrpc":"2.0","id":null,"error":{"code":-32603,"message":"failed to serialize error response"}}"#.to_vec())
+        .expect("Response::Error serialization is infallible")
         .into()
 }