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/session/context_window.rs

@@ -31,7 +31,7 @@ pub(crate) async fn context_window_token_status(
         match turn_context.config.model_auto_compact_token_limit_scope {
             AutoCompactTokenLimitScope::Total => (
                 active_context_tokens,
-                turn_context.model_info.auto_compact_token_limit(),
+                turn_context.model_info().auto_compact_token_limit(),
                 None,
             ),
             AutoCompactTokenLimitScope::BodyAfterPrefix => {
@@ -41,7 +41,7 @@ pub(crate) async fn context_window_token_status(
                 let scope_limit = turn_context
                     .config
                     .model_auto_compact_token_limit
-                    .or_else(|| turn_context.model_info.auto_compact_token_limit());
+                    .or_else(|| turn_context.model_info().auto_compact_token_limit());
                 (
                     active_context_tokens.saturating_sub(baseline),
                     scope_limit,