Support model catalog overrides for plugin guidance (#58894)

## What changed

- Add `model_messages.plugins` overrides for generic usage guidance, selected-plugin hints, and recommendation introductions, with independent fallback to bundled wording for missing or invalid fields.
- Validate text limits and required template placeholders while keeping plugin identities, available capabilities, and eligibility controlled by the client.
- Track generic guidance changes across model switches and session resume, emitting replacement or retirement notices and supporting legacy snapshots and retained history.

## Testing

Add unit and scenario coverage for sparse overrides, literal text preservation, template validation, UTF-8 size bounds, capability filtering, recommendation fallback, and guidance recovery after resume.

GitOrigin-RevId: 148b658c2d8490c9d0dc208addbee1be5342a5f5

codex-rs/core/src/session/mod.rs

@@ -4983,7 +4983,13 @@ impl Session {
             if next_item.is_none()
                 && let Some(recommended_plugins) = recommended_plugin_candidates
                     .as_deref()
-                    .and_then(RecommendedPluginsInstructions::from_plugins)
+                    .and_then(|plugins| {
+                        RecommendedPluginsInstructions::from_plugins(
+                            plugins,
+                            &ResolvedModelMessages::from_model(&step_context.settings.model_info)
+                                .plugin_recommendations(),
+                        )
+                    })
             {
                 developer_sections.push(recommended_plugins.render_fragment());
             }

codex-rs/core/src/session/turn.rs

@@ -1271,6 +1271,7 @@ async fn build_skills_and_plugins(
         mcp_tools,
         &available_connectors,
         &turn_context.config.features,
+        codex_prompts::ResolvedModelMessages::from_model(&step_context.settings.model_info),
     );
     let mut explicitly_enabled_connectors = collect_explicit_app_ids(user_input);
     explicitly_enabled_connectors.extend(skill_connector_ids);

codex-rs/core/src/session/world_state.rs

@@ -342,9 +342,15 @@ impl Session {
         ));
         let plugins_usage_instructions_available =
             step_context.mcp.plugins_available() && model_info.include_plugin_usage_instructions;
-        world_state.add_section(PluginsInstructionsState::new(
-            plugins_usage_instructions_available,
-        ));
+        let plugins_state = {
+            let state = self.state.lock().await;
+            PluginsInstructionsState::new(
+                plugins_usage_instructions_available,
+                model_messages.generic_plugin(),
+                state.history.raw_items(),
+            )
+        };
+        world_state.add_section(plugins_state);
         if turn_context
             .config
             .features