Expand preprocessor documentation with detailed guides

[mintlify]

Summary

• Significantly expanded the preprocessor documentation page (both English and Chinese versions) with comprehensive, detailed content
• Added in-depth sections for each preprocessor type: Canny, Depth Estimation (Depth Anything V2, MiDaS, ZoeDepth), OpenPose (body/hand/face detection modes), Lineart (standard/anime/coarse), and Normal Map
• Added additional preprocessor overviews: Scribble, SoftEdge/HED, Segmentation, MLSD
• Included a preprocessor selection guide table and combination recommendations
• Added technical details such as working principles, key parameters, comparison tables, and practical usage tips
• Maintained all existing workflow links (Comfy Cloud and download)

[mintlify]

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Project	Status	Preview	Updated (UTC)
comfy	🟢 Ready	View Preview	Apr 16, 2026, 10:53 AM

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