feat(editor): release callout (#13896)

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

* **Refactor**
* Callout is no longer gated as an experimental option — it now
consistently appears in the editor’s slash menu and toolbar where
applicable.

* **Tests**
* End-to-end slash-menu tests updated to expect the Callout item in
search results and adjusted item ordering.

* **Chores**
  * Repository ignore rules updated to exclude .kiro files.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/modules/feature-flag/constant.ts

@@ -95,16 +95,6 @@ export const AFFINE_FLAGS = {
     configurable: isCanaryBuild,
     defaultState: true,
   },
-  enable_callout: {
-    category: 'blocksuite',
-    bsFlag: 'enable_callout',
-    displayName:
-      'com.affine.settings.workspace.experimental-features.enable-callout.name',
-    description:
-      'com.affine.settings.workspace.experimental-features.enable-callout.description',
-    configurable: isCanaryBuild,
-    defaultState: isCanaryBuild,
-  },
 
   enable_emoji_folder_icon: {
     category: 'affine',