Finalize model-specific tool plans in ToolRouter (#41195)

## Why

Planning tools for a candidate model must not change the selected model or its
Responses Lite tool inventory. Otherwise, preparing a fallback can overwrite
metadata before the current model's request is sent.

## What changed

- Build tool registries and visible specs from an explicit `ModelInfo`.
- Store the finalized tool mode, code-mode names, namespace inventory, and
  terminal and child-management capabilities on `ToolRouter`.
- Publish namespace inventory only after selecting the step's router, and use
  that router's mode when dispatching and recording tool calls.

## Testing

Added coverage for candidate-model isolation, fallback compaction metadata,
code-mode worker selection, normalized tool names, and router capabilities.

GitOrigin-RevId: 56df2de8f42c7e93a4c4dcd117720e40a0cca3db

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

@@ -3398,6 +3398,8 @@ impl Session {
         let tool_router = turn::built_tools(
             self.as_ref(),
             turn_context.as_ref(),
+            // TODO(CDXENT-441): use the step scoped model
+            turn_context.model_info(),
             &environments,
             &mcp,
             &extension_data,
@@ -3405,6 +3407,21 @@ impl Session {
         )
         .or_cancel(cancellation_token)
         .await??;
+        // Publish inventory after planning rather than during finalization, so constructing
+        // additional candidate plans cannot overwrite turn-wide metadata.
+        if turn_context
+            .config
+            .tool_registry
+            .turn_metadata_includes_tool_info
+            && turn_context.model_info().use_responses_lite
+        {
+            turn_context.turn_metadata_state.set_tool_namespaces_info(
+                tool_router
+                    .tool_namespaces_info()
+                    .cloned()
+                    .unwrap_or_default(),
+            );
+        }
         Ok(Arc::new(StepContext {
             settings,
             token_budget,