Persist target default reasoning on model upgrade

[shijie-oai]

Why

When the TUI upgrade flow moves a user to a newer model, the accepted migration should also persist the target model's default reasoning effort. That keeps the upgraded model and reasoning setting aligned instead of carrying forward a stale previously saved effort from the old model.

What changed

• The accepted model migration path now updates in-memory config, TUI state, and persisted model selection with the target preset's default_reasoning_effort.
• The upgrade destructuring keeps reasoning_effort_mapping explicitly unused because mappings are no longer consulted on accepted migrations.
• Added a catalog test that starts with a pre-existing saved reasoning effort and verifies the accepted upgrade overwrites it with the target model default and emits the expected persistence events.
• Rebasing onto current main also updates a TUI thread-session test helper for the latest permission_profile field and ApprovalsReviewer::AutoReview rename so CI compiles on the new base.

Verification

• cargo test -p codex-tui model_catalog
• cargo test -p codex-tui permission_settings_sync_updates_active_snapshot_without_rewriting_side_thread