feat(editor): add mermaid code preview (#13456)

<img width="971" height="681" alt="iShot_2025-08-10_14 29 01"
src="https://github.com/user-attachments/assets/eff3e6d5-3129-42ac-aceb-994c18f675ab"
/>


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

* **New Features**
* Mermaid diagram previews for code blocks with interactive zoom, pan,
and reset controls.
* Improved rendering feedback with loading, error states, retry
behavior, and fallback messaging.

* **Chores**
  * Added Mermaid as a frontend dependency to enable diagram rendering.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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Co-authored-by: L-Sun <zover.v@gmail.com>

packages/frontend/core/src/components/hooks/affine/use-ai-specs.ts

@@ -44,7 +44,7 @@ export const useAISpecs = () => {
       .mobile(framework)
       .electron(framework)
       .linkPreview(framework)
-      .codeBlockHtmlPreview(framework).value;
+      .codeBlockPreview(framework).value;
 
     return manager.get('page');
   }, [