fix: slim initrd + smaller image for fast USB boot
- Set includeDefaultModules=false — only load Intel laptop + USB boot
modules instead of every driver. Drops initrd from 1.4GB to ~50-80MB.
- Reduce additionalSpace from 2G to 256M (read-only kiosk).
- Should cut loader time from 55s to ~5s on USB2.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>