Optimize GIF encoding with max width scaling and color limiting

[grovecj]

Summary

• Max width scaling (default 800px) — large captures are downscaled proportionally using lanczos resampling, never upscaled
• Color palette limiting — wires up the existing colors config (default changed from 256 to 128) to ffmpeg's palettegen=max_colors
• Bayer dithering — adds ordered dithering for better visual quality at reduced color counts; compresses better than floyd_steinberg in GIF format
• Expected file size reduction: 70–80%

Configuration

Users can tune via config.json:

"encoding": {
  "colors": 128,
  "maxWidth": 800
}

• colors: 16–256 (fewer = smaller files, lower quality)
• maxWidth: 320–3840 (smaller = smaller files)

Test plan

• Capture a large region (fullscreen on high-DPI) and compare file size to previous
• Verify quality is acceptable at 128 colors / 800px
• Test small capture (< 800px) is not upscaled
• Test with colors: 256, maxWidth: 3840 for max quality

🤖 Generated with Claude Code