feat: support video cell first frame snapshot

[Semlaw]

feat: support video cell first frame snapshot

🤔 This is a ...

• New feature
• Bug fix
• TypeScript definition update
• Bundle size optimization
• Performance optimization
• Enhancement feature
• Refactoring
• Update dependency
• Code style optimization
• Test Case
• Branch merge
• Site / documentation update
• Demo update
• Workflow
• Chore
• Release
• Other (about what?)

🔗 Related issue link

N/A

💡 Background and solution

This PR adds an optional video cell first-frame snapshot mode.

When customConfig.videoFirstFrameSnapshot is enabled, the video cell captures the loaded first frame into a canvas, replaces the video element with the canvas image, and releases the video resource. This reduces long-lived video element usage after the first frame has been rendered.

New options:

customConfig: {
  videoFirstFrameSnapshot?: boolean;
  videoFirstFrameTimeout?: number;
  videoFirstFrameMaxCanvasSize?: number;
}

It also improves video load failure handling by keeping the video damage image aspect ratio immediately after load errors and after column resize.

📝 Changelog

Language	Changelog
🇺🇸 English	Add optional first-frame canvas snapshot support for video cells and release video resources after snapshot.
🇨🇳 Chinese	新增视频单元格首帧 canvas 快照配置，快照完成后释放 video 资源。

☑️ Self-Check before Merge

⚠️ Please check all items below before requesting a reviewing. ⚠️

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

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🚀 Summary

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🔍 Walkthrough

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