Pretty plugin labels, preserve plugin app provenance during MCP tool refresh (#15606)

- Prefer plugin manifest `interface.displayName` for plugin labels.
- Preserve plugin provenance when handling `list_mcp_tools` so connector
`plugin_display_names` are not clobbered.
- Add a TUI test to ensure plugin-owned app mentions are deduped
correctly.

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

@@ -1550,7 +1550,14 @@ fn load_plugin(
     };
 
     let manifest_paths = &manifest.paths;
-    loaded_plugin.manifest_name = Some(manifest.name.clone());
+    loaded_plugin.manifest_name = manifest
+        .interface
+        .as_ref()
+        .and_then(|interface| interface.display_name.as_deref())
+        .map(str::trim)
+        .filter(|display_name| !display_name.is_empty())
+        .map(str::to_string)
+        .or_else(|| Some(manifest.name.clone()));
     loaded_plugin.manifest_description = manifest.description.clone();
     loaded_plugin.skill_roots = plugin_skill_roots(plugin_root.as_path(), manifest_paths);
     let resolved_skills = load_plugin_skills(