Remove response.processed websocket request (#26447)

## Why

The Responses websocket client no longer needs to send a follow-up
`response.processed` request after a turn response has already been
recorded. Keeping that extra acknowledgement path adds feature-gated
control flow and a second websocket request shape that no longer carries
useful behavior.

## What Changed

- Removed the `response.processed` websocket request type and sender.
- Removed the `responses_websocket_response_processed` feature flag and
schema entry.
- Removed turn and remote-compaction plumbing that only tracked response
IDs to send the acknowledgement.
- Removed tests that existed solely to cover the deleted feature path.

## Validation

- `just fix -p codex-core -p codex-api -p codex-features`

codex-rs/codex-api/src/common.rs

@@ -239,11 +239,6 @@ pub struct ResponseCreateWsRequest {
     pub client_metadata: Option<HashMap<String, String>>,
 }
 
-#[derive(Debug, Serialize)]
-pub struct ResponseProcessedWsRequest {
-    pub response_id: String,
-}
-
 pub fn response_create_client_metadata(
     client_metadata: Option<HashMap<String, String>>,
     trace: Option<&W3cTraceContext>,
@@ -272,8 +267,6 @@ pub fn response_create_client_metadata(
 pub enum ResponsesWsRequest {
     #[serde(rename = "response.create")]
     ResponseCreate(ResponseCreateWsRequest),
-    #[serde(rename = "response.processed")]
-    ResponseProcessed(ResponseProcessedWsRequest),
 }
 
 pub fn create_text_param_for_request(

codex-rs/codex-api/src/endpoint/responses_websocket.rs

@@ -1,6 +1,5 @@
 use crate::auth::SharedAuthProvider;
 use crate::common::ResponseEvent;
-use crate::common::ResponseProcessedWsRequest;
 use crate::common::ResponseStream;
 use crate::common::ResponsesWsRequest;
 use crate::error::ApiError;
@@ -206,40 +205,6 @@ impl ResponsesWebsocketConnection {
         self.stream.lock().await.is_none()
     }
 
-    #[instrument(
-        name = "responses_websocket.send_response_processed",
-        level = "info",
-        skip_all,
-        fields(transport = "responses_websocket", api.path = "responses")
-    )]
-    #[expect(
-        clippy::await_holding_invalid_type,
-        reason = "the guard serializes exclusive use of the websocket while sending a request frame"
-    )]
-    pub async fn send_response_processed(&self, response_id: String) -> Result<(), ApiError> {
-        let request =
-            ResponsesWsRequest::ResponseProcessed(ResponseProcessedWsRequest { response_id });
-        let request_body = serde_json::to_value(&request).map_err(|err| {
-            ApiError::Stream(format!("failed to encode websocket request: {err}"))
-        })?;
-
-        let mut guard = self.stream.lock().await;
-        let Some(ws_stream) = guard.as_mut() else {
-            return Err(ApiError::Stream(
-                "websocket connection is closed".to_string(),
-            ));
-        };
-
-        send_websocket_request(
-            ws_stream,
-            request_body,
-            self.idle_timeout,
-            self.telemetry.as_ref(),
-            /*connection_reused*/ true,
-        )
-        .await
-    }
-
     #[instrument(
         name = "responses_websocket.stream_request",
         level = "info",

codex-rs/codex-api/src/lib.rs

@@ -32,7 +32,6 @@ pub use crate::common::RawMemoryMetadata;
 pub use crate::common::Reasoning;
 pub use crate::common::ResponseCreateWsRequest;
 pub use crate::common::ResponseEvent;
-pub use crate::common::ResponseProcessedWsRequest;
 pub use crate::common::ResponseStream;
 pub use crate::common::ResponsesApiRequest;
 pub use crate::common::ResponsesWsRequest;