[3 of 7] Remove UserTurn (#23075)

**Stack position:** [3 of 7]

## Summary

This PR finishes the input-op consolidation by moving the remaining
`Op::UserTurn` callers onto `Op::UserInput` and deleting `Op::UserTurn`.
This touches a lot of files, but it is a low-risk mechanical migration.

## Stack

1. [1 of 7] [Add thread settings to
UserInput](https://github.com/openai/codex/pull/23080)
2. [2 of 7] [Remove
UserInputWithTurnContext](https://github.com/openai/codex/pull/23081)
3. [3 of 7] [Remove
UserTurn](https://github.com/openai/codex/pull/23075) (this PR)
4. [4 of 7] [Placeholder for OverrideTurnContext
cleanup](https://github.com/openai/codex/pull/23087)
5. [5 of 7] [Replace OverrideTurnContext with
ThreadSettings](https://github.com/openai/codex/pull/22508)
6. [6 of 7] [Add app-server thread settings
API](https://github.com/openai/codex/pull/22509)
7. [7 of 7] [Sync TUI thread
settings](https://github.com/openai/codex/pull/22510)

codex-rs/core/src/session/handlers.rs

@@ -49,9 +49,6 @@ use codex_protocol::request_permissions::RequestPermissionsResponse;
 use codex_protocol::request_user_input::RequestUserInputResponse;
 
 use crate::context_manager::is_user_turn_boundary;
-use codex_protocol::config_types::CollaborationMode;
-use codex_protocol::config_types::ModeKind;
-use codex_protocol::config_types::Settings;
 use codex_protocol::dynamic_tools::DynamicToolResponse;
 use codex_protocol::items::UserMessageItem;
 use codex_protocol::mcp::RequestId as ProtocolRequestId;
@@ -114,56 +111,6 @@ pub(super) async fn user_input_or_turn_inner(
     mirror_user_text_to_realtime: Option<()>,
 ) {
     let (items, updates, responsesapi_client_metadata) = match op {
-        Op::UserTurn {
-            cwd,
-            approval_policy,
-            approvals_reviewer,
-            sandbox_policy,
-            permission_profile,
-            model,
-            effort,
-            summary,
-            service_tier,
-            final_output_json_schema,
-            items,
-            collaboration_mode,
-            personality,
-            environments,
-        } => {
-            let collaboration_mode = collaboration_mode.or_else(|| {
-                Some(CollaborationMode {
-                    mode: ModeKind::Default,
-                    settings: Settings {
-                        model: model.clone(),
-                        reasoning_effort: effort,
-                        developer_instructions: None,
-                    },
-                })
-            });
-            (
-                items,
-                SessionSettingsUpdate {
-                    cwd: Some(cwd),
-                    approval_policy: Some(approval_policy),
-                    approvals_reviewer,
-                    sandbox_policy: Some(sandbox_policy),
-                    workspace_roots: None,
-                    profile_workspace_roots: None,
-                    permission_profile,
-                    active_permission_profile: None,
-                    windows_sandbox_level: None,
-                    collaboration_mode,
-                    reasoning_summary: summary,
-                    service_tier,
-                    final_output_json_schema: Some(final_output_json_schema),
-                    environments,
-                    personality,
-                    app_server_client_name: None,
-                    app_server_client_version: None,
-                },
-                None,
-            )
-        }
         Op::UserInput {
             items,
             environments,
@@ -826,7 +773,7 @@ pub(super) async fn submission_loop(
                     .await;
                     false
                 }
-                Op::UserInput { .. } | Op::UserTurn { .. } => {
+                Op::UserInput { .. } => {
                     user_input_or_turn(&sess, sub.id.clone(), sub.op).await;
                     false
                 }

codex-rs/core/src/session/tests.rs

@@ -5197,7 +5197,7 @@ fn submission_dispatch_span_uses_debug_for_realtime_audio() {
 }
 
 #[test]
-fn op_kind_distinguishes_turn_ops() {
+fn op_kind_for_input_and_context_ops() {
     assert_eq!(
         Op::OverrideTurnContext {
             cwd: None,
@@ -5237,24 +5237,31 @@ async fn user_turn_updates_approvals_reviewer() {
     handlers::user_input_or_turn(
         &session,
         "sub-1".to_string(),
-        Op::UserTurn {
-            environments: None,
+        Op::UserInput {
             items: vec![UserInput::Text {
                 text: "hello".to_string(),
                 text_elements: Vec::new(),
             }],
-            cwd: config.cwd.to_path_buf(),
-            approval_policy: config.permissions.approval_policy.value(),
-            approvals_reviewer: Some(codex_config::types::ApprovalsReviewer::AutoReview),
-            sandbox_policy: config.legacy_sandbox_policy(),
-            permission_profile: None,
-            model: turn_context.model_info.slug.clone(),
-            effort: config.model_reasoning_effort,
-            summary: config.model_reasoning_summary,
-            service_tier: None,
+            environments: None,
             final_output_json_schema: None,
-            collaboration_mode: None,
-            personality: config.personality,
+            responsesapi_client_metadata: None,
+            thread_settings: codex_protocol::protocol::ThreadSettingsOverrides {
+                cwd: Some(config.cwd.to_path_buf()),
+                approval_policy: Some(config.permissions.approval_policy.value()),
+                approvals_reviewer: Some(codex_config::types::ApprovalsReviewer::AutoReview),
+                sandbox_policy: Some(config.legacy_sandbox_policy()),
+                summary: config.model_reasoning_summary,
+                personality: config.personality,
+                collaboration_mode: Some(codex_protocol::config_types::CollaborationMode {
+                    mode: codex_protocol::config_types::ModeKind::Default,
+                    settings: codex_protocol::config_types::Settings {
+                        model: turn_context.model_info.slug.clone(),
+                        reasoning_effort: config.model_reasoning_effort,
+                        developer_instructions: None,
+                    },
+                }),
+                ..Default::default()
+            },
         },
     )
     .await;