feat(core): add gemini callout syntax highlighting (#12413)

Close [AI-125](https://linear.app/affine-design/issue/AI-125)

What Changed?
- Add `gemini-2.5-flash-preview-04-17` model
- Add `thinkingConfig` provider options
- Add callout syntax highlighting

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

- **New Features**
  - Added support for the "Gemini 2.5 Flash" model and updated the "Gemini 2.5 Pro" model to a newer version.
  - Enhanced streaming responses to better format reasoning outputs and provide clearer callouts in AI-generated content.

- **Bug Fixes**
  - Improved audio transcription prompts in test cases for more accurate and explicit testing.

- **Documentation**
  - Expanded citation instructions for AI chat responses, including examples for multiple citations.

- **Chores**
  - Updated the "@ai-sdk/google" dependency to a newer version.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

yarn.lock

@@ -908,7 +908,7 @@ __metadata:
     "@affine/reader": "workspace:*"
     "@affine/server-native": "workspace:*"
     "@ai-sdk/anthropic": "npm:^1.2.10"
-    "@ai-sdk/google": "npm:^1.2.10"
+    "@ai-sdk/google": "npm:^1.2.18"
     "@ai-sdk/openai": "npm:^1.3.21"
     "@ai-sdk/perplexity": "npm:^1.1.6"
     "@apollo/server": "npm:^4.11.3"
@@ -1083,7 +1083,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@ai-sdk/google@npm:^1.2.10":
+"@ai-sdk/google@npm:^1.2.18":
   version: 1.2.18
   resolution: "@ai-sdk/google@npm:1.2.18"
   dependencies: