feat: remove background

CLAUDE.md

@@ -12,6 +12,7 @@ npm run build:css:watch    # Watch mode for CSS
 npm run preview            # Serve HTML at localhost:3000
 npm run dev                # CSS watch + preview server (concurrent)
 npm run pdf -- <file>      # Convert HTML file to PDF
+npm run remove-bg -- <file|dir>  # Remove white background from PNG icons
 ```
 
 Generate images via Banatie API:
@@ -30,6 +31,7 @@ src/
   scripts/
     generate-pdf.mjs           — HTML → PDF via Puppeteer
     banatie.mjs                — Banatie API client for image generation
+    remove-bg.mjs              — Remove white background from PNGs (flood fill)
 tasks/                         — JSON task definition files
 assets/
   hero-images/                 — spaceship1-6.jpeg (header hero images)
@@ -154,6 +156,20 @@ REST API for generating images.
 
 Configuration is in `src/scripts/banatie.mjs`. Set the `BANATIE_API_KEY` environment variable for authentication.
 
+## Background Removal
+
+Script `src/scripts/remove-bg.mjs` removes white backgrounds from PNG icons using flood-fill from edges (like magic wand in Photoshop). Uses sharp. White areas inside objects are preserved.
+
+```bash
+node src/scripts/remove-bg.mjs <file|dir> [--threshold N] [--fuzz N]
+```
+
+- `--threshold` — whiteness threshold for R,G,B (default: 230, lower = more aggressive)
+- `--fuzz` — anti-alias radius in pixels at the boundary (default: 0)
+- Default input: `assets/icons/pack2/`
+
+This is optional — not all icons need it. After generating/splitting new icons, ask the user if they want background removal on specific files.
+
 ## PDF Generation
 
 Puppeteer settings for A4 worksheets: