Allow per-turn overrides for direct-only tool namespaces (#59481)

## What changed

- Add `direct_only_tool_namespaces` to `TurnStartOptions`. Omission inherits the thread configuration; an empty list clears direct-only routing for that turn. Steering ignores the option.
- Persist explicit overrides in turn context and restore them when recovering an interrupted turn, including turns started by standalone tool output.
- Keep subsequent turns and spawned or resumed child agents on the thread's routing defaults.

## Testing

Add coverage for routing changes across turns in Responses and Responses Lite, recovery without carrying overrides into subsequent turns, and child-agent inheritance.

GitOrigin-RevId: cea1a997424572d4cd372cd15b098626904c6796

codex-rs/state/src/extract.rs

@@ -578,6 +578,7 @@ mod tests {
             &RolloutItem::TurnContext(TurnContextItem {
                 turn_id: Some("turn-1".to_string()),
                 root_turn_id: None,
+                direct_only_tool_namespaces: None,
                 disabled_plugin_ids: None,
                 cwd: serde_json::from_value(serde_json::json!(
                     std::env::current_dir()
@@ -622,6 +623,7 @@ mod tests {
             &RolloutItem::TurnContext(TurnContextItem {
                 turn_id: Some("turn-1".to_string()),
                 root_turn_id: None,
+                direct_only_tool_namespaces: None,
                 disabled_plugin_ids: None,
                 cwd: serde_json::from_value(serde_json::json!(
                     std::env::current_dir()
@@ -666,6 +668,7 @@ mod tests {
             &RolloutItem::TurnContext(TurnContextItem {
                 turn_id: Some("turn-1".to_string()),
                 root_turn_id: None,
+                direct_only_tool_namespaces: None,
                 disabled_plugin_ids: None,
                 cwd: serde_json::from_value(serde_json::json!(&fallback_cwd))
                     .expect("absolute fallback cwd"),
@@ -699,6 +702,7 @@ mod tests {
             &RolloutItem::TurnContext(TurnContextItem {
                 turn_id: Some("turn-1".to_string()),
                 root_turn_id: None,
+                direct_only_tool_namespaces: None,
                 disabled_plugin_ids: None,
                 cwd: serde_json::from_value(serde_json::json!(
                     std::env::current_dir()