fix(editor): add comment entire to inner toolbar (#13304)

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[BS-3624](https://linear.app/affine-design/issue/BS-3624/page模式单选图片的时候希望有comment-按钮)




#### PR Dependency Tree


* **PR #13304** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added a comment button to the image and surface reference block
toolbars for easier commenting.

* **Refactor**
* Simplified array flattening operations across multiple components and
utilities by replacing `.map(...).flat()` with `.flatMap(...)`,
improving code readability and maintainability.

* **Bug Fixes**
* Improved comment creation logic to allow adding comments even when
selections exist.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/widgets/slash-menu/src/slash-menu-popover.ts

@@ -142,15 +142,13 @@ export class SlashMenu extends WithDisposable(LitElement) {
       // We search first and second layer
       if (this._filteredItems.length !== 0 && depth >= 1) break;
 
-      queue = queue
-        .map<typeof queue>(item => {
-          if (isSubMenuItem(item)) {
-            return item.subMenu;
-          } else {
-            return [];
-          }
-        })
-        .flat();
+      queue = queue.flatMap(item => {
+        if (isSubMenuItem(item)) {
+          return item.subMenu;
+        } else {
+          return [];
+        }
+      });
 
       depth++;
     }