Support Daybreak selection in codex exec (#49856)

## What changed

- Add the `daybreak` configuration key, defaulting to `false`, with per-invocation overrides such as `-c daybreak=true`.
- Resolve access programs from the model catalog, preferring `daybreak_blue` over `daybreak_red` when enabled and selecting advertised `standard` access when disabled for signed-in ChatGPT accounts. Require the OpenAI provider, a signed-in ChatGPT account, and a compatible model to enable Daybreak.
- Save the choice for new persistent threads and inherit it on resume and fork, including ephemeral forks. Explicit CLI overrides apply only to the current invocation.

## Testing

Add protocol tests for advertised-program selection and exec integration tests for account and provider restrictions, saved choices, ephemeral forks, and invocation-only overrides.

GitOrigin-RevId: ac955f08b5a891e720cfc5f67fabb7b0f6d32bb8

codex-rs/thread-manager-sample/src/main.rs

@@ -242,6 +242,7 @@ async fn new_config(
         startup_warnings: Vec::new(),
         bypass_hook_trust: false,
         model,
+        daybreak_enabled: false,
         service_tier: None,
         review_model: None,
         model_context_window: None,