Support model catalog Apps usage instructions (#61213)

## What changed

- Add the disabled-by-default `catalog_apps_instructions` feature to use the selected model's `model_messages.apps.usage_instructions`, subject to existing Apps availability and model gates.
- Preserve valid catalog text literally, allow an empty string to clear guidance, and fall back to bundled instructions for missing, whitespace-only, or oversized values. Overrides are limited to 800 UTF-8 bytes.
- Reconcile guidance with the latest retained Apps fragment, emitting replacement or removal notices when needed and avoiding repeated updates across resumes. Preserve compatibility with bundled guidance and legacy checkpoints.
- Recognize catalog Apps fragments as contextual developer messages in event mapping and rollout rollback.

## Testing

Add resolver, world-state, client, and scenario coverage for literal text and byte limits, feature and availability gates, model switches, clearing guidance, resumes, and legacy history recovery.

GitOrigin-RevId: 6240d407ada8f22fa101753ff3ddb338632ae283

codex-rs/thread-store/src/local/rollout_migration/rollback.rs

@@ -11,6 +11,8 @@
 use codex_protocol::items::parse_hook_prompt_fragment;
 use codex_protocol::models::ContentItem;
 use codex_protocol::models::ResponseItem;
+use codex_protocol::protocol::APPS_INSTRUCTIONS_OPEN_TAG;
+use codex_protocol::protocol::CATALOG_APPS_INSTRUCTIONS_OPEN_TAG;
 use codex_protocol::protocol::InterAgentCommunication;
 use std::borrow::Borrow;
 
@@ -89,7 +91,8 @@ fn is_known_contextual_developer_message_content(content: &[ContentItem]) -> boo
             "<permissions instructions>",
             "<model_switch>",
             "<managed_developer_instructions>",
-            "<apps_instructions>",
+            APPS_INSTRUCTIONS_OPEN_TAG,
+            CATALOG_APPS_INSTRUCTIONS_OPEN_TAG,
             "<collaboration_mode>",
             "<multi_agent_mode>",
             "<environments_instructions>",

codex-rs/thread-store/src/local/rollout_migration_tests.rs

@@ -942,6 +942,10 @@ async fn migration_rolls_back_response_and_inter_agent_user_boundaries() {
                 "developer",
                 "<managed_developer_instructions>context only</managed_developer_instructions>",
             )),
+            rollout_response_item(input_response_message(
+                "developer",
+                "<catalog_apps_instructions>context only</catalog_apps_instructions>",
+            )),
             rollout_response_item(input_response_message(
                 "developer",
                 "<permissions instructions>context only</permissions instructions>",