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/core/src/tasks/mod.rs

@@ -556,6 +556,7 @@ impl Session {
                 .and_then(|context| context.cyber_access_program);
         }
         let options = NewTurnContextOptions {
+            direct_only_tool_namespaces: start_options.direct_only_tool_namespaces,
             final_output_json_schema: start_options.final_output_json_schema,
             prompt_cache_ttl: start_options.prompt_cache_ttl,
             cyber_access_program: start_options.cyber_access_program,