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 -->

blocksuite/affine/shared/src/services/feature-flag-service.ts

@@ -17,7 +17,6 @@ export interface BlockSuiteFlags {
   enable_mobile_linked_doc_menu: boolean;
   enable_mobile_database_editing: boolean;
   enable_block_meta: boolean;
-  enable_callout: boolean;
   enable_edgeless_scribbled_style: boolean;
   enable_table_virtual_scroll: boolean;
   enable_turbo_renderer: boolean;
@@ -43,7 +42,6 @@ export class FeatureFlagService extends StoreExtension {
     enable_mobile_linked_doc_menu: false,
     enable_block_meta: true,
     enable_mobile_database_editing: false,
-    enable_callout: false,
     enable_edgeless_scribbled_style: false,
     enable_table_virtual_scroll: false,
     enable_turbo_renderer: false,