Close [AI-126](https://linear.app/affine-design/issue/AI-126)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Introduced a new web crawling tool, allowing users to extract live content from specific web pages in addition to traditional web search.
- **Improvements**
- Enhanced error handling for web search and web crawl operations, providing clearer failure messages.
- Updated terminology in AI prompts and user-facing messages to reflect the new web search/crawl capabilities.
- Improved formatting of web search and crawl results for better readability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Close [AI-75](https://linear.app/affine-design/issue/AI-75)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Improved formatting for AI-generated reasoning and web search results, displaying them as callout blocks for enhanced readability.
- Expanded support for rendering callout blocks in the text renderer.
- **Style**
- Adjusted layout to ensure callout blocks retain appropriate spacing and appearance.
- **Refactor**
- Simplified and unified the integration of web search tools for AI providers.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Close [AI-85](https://linear.app/affine-design/issue/AI-85)
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Enhanced AI chat experience with improved web search integration, including a new "AUTO" mode that allows the AI to search the web only when needed.
- Updated AI model for chat to "o4-mini" for improved performance.
- **Improvements**
- Refined instructions to reduce hallucinations and ensure the AI admits uncertainty when unsure.
- Enhanced streaming responses to display web search queries and results more clearly.
- Updated web search tool modes for more accurate and flexible search behavior.
- Centralized AI provider options and improved tool selection logic for better response quality.
- **Bug Fixes**
- Improved handling of tool calls and reasoning steps in AI chat responses.
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