Preserve plugin caches across display metadata refreshes (#46309)

## Why

Renewed image URLs and other display metadata changes unnecessarily invalidate loaded plugins and MCP and skill caches, even when installed plugin behavior is unchanged.

## What changed

- Compare installed plugin metadata by identity, version, enablement, policy, and availability before invalidating derived caches. Continue storing the full updated payload so display consumers receive fresh metadata.
- Preserve invalidation when behavioral metadata changes or reconciliation requires an effective plugin refresh.
- Export `remote_catalog_metadata_eq` to compare catalogs independently of display metadata and plugin display order, while retaining marketplace order significance.

## Testing

Add regression tests for display-only updates, behavioral changes, catalog ordering, and preservation of loaded skills and tool suggestions. Add an app-server integration test verifying that image URL renewals and badge updates preserve live MCP sessions and cached skill resources, while an authentication policy change invalidates resource caches.

GitOrigin-RevId: 22b9ba1234a9f850201c6890e03d1ef899a56c54

codex-rs/core-plugins/src/manager.rs

@@ -1417,10 +1417,16 @@ impl PluginsManager {
             }
             return Some(needs_effective_plugins_refresh);
         }
+        let metadata_changed = cache.plugins.as_ref().is_none_or(|previous| {
+            !crate::remote_metadata::installed_plugin_metadata_eq(previous, &plugins)
+        });
         cache.plugins = Some(plugins);
         drop(cache);
-        self.clear_loaded_plugins_cache();
-        Some(true)
+        let changed = needs_effective_plugins_refresh || metadata_changed;
+        if changed {
+            self.clear_loaded_plugins_cache();
+        }
+        Some(changed)
     }
 
     #[cfg(test)]