Snapshot resolved settings for each model step (#40651)

## Why

Thread settings can change while a turn is running, and delegated review or
compaction steps can select a different model. Each request needs a consistent
set of settings resolved against the model that will execute it.

## What changed

- Capture immutable resolved settings for each model step, including model
  metadata, reasoning options, service tier, approvals, and personality.
- Keep in-flight steps on their captured settings while applying thread updates
  to subsequent work.
- Resolve inherited reasoning summaries and filter service tiers against the
  selected model and feature configuration for review and compaction steps.

## Testing

Added coverage for settings updates during paused turns, model changes,
previous-model compaction, review-model defaults, and service-tier filtering.

GitOrigin-RevId: fca4b3b305379f1bf26a5cac75ee0dd1747ac1f6

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

@@ -65,7 +65,7 @@ pub(crate) fn tool_user_shell_type(
 }
 
 pub(crate) fn requested_tool_mode(turn_context: &TurnContext) -> ToolMode {
-    turn_context.model_info.tool_mode.unwrap_or_else(|| {
+    turn_context.model_info().tool_mode.unwrap_or_else(|| {
         if turn_context.config.features.enabled(Feature::CodeModeOnly) {
             ToolMode::CodeModeOnly
         } else if turn_context.config.features.enabled(Feature::CodeMode) {