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/models-manager/src/model_info_tests.rs

@@ -41,6 +41,7 @@ fn base_instruction_override_is_literal_and_preserves_catalog_messages() {
             prompted_categories: Some("Allowed: {{ categories }}".to_string()),
             rejected_categories: Some("Denied: {{ categories }}".to_string()),
         }),
+        ..Default::default()
     };
     let collaboration_modes = CollaborationModeMessages {
         default: Some("default instructions".to_string()),
@@ -174,6 +175,7 @@ fn personality_none_strips_catalog_instruction_sources_through_the_next_h1() {
                 never: None,
                 unless_trusted: None,
                 granular: None,
+                ..Default::default()
             }),
             ..Default::default()
         };