Allow model catalogs to customize approval instruction headings (#57581)

## What changed

Add optional `request_permissions` and `auto_review_suffix` fields to catalog approval messages. Use them to customize the permission tool heading and introduce automatic review guidance while preserving the bundled instruction bodies and existing policy gates. Accept `request_permissions_tool` as a deserialization alias.

Limit headings to 500 UTF-8 bytes on a single line and fall back to bundled text for missing or invalid values. Complete catalog approval messages retain precedence.

## Testing

Add coverage for heading validation, serialization aliases, policy gates, fallback behavior, and complete-message precedence. Integration tests verify that model switches append the selected model's headings without rewriting history or repeating unchanged instructions.

GitOrigin-RevId: 3311591a464cc086783fe25271a352dd5a229790

codex-rs/core/src/context/world_state/permissions_tests.rs

@@ -264,6 +264,7 @@ fn permissions_state(
         never: None,
         unless_trusted: None,
         granular: None,
+        ..Default::default()
     };
     let permission_messages = PermissionMessages {
         danger_full_access: Some("Full access.".to_string()),