- live-mask.spec.ts: replace green-overlay avgAlpha assertions with
checkerboard + slab pixel detection; add green-overlay color rejection
check; fix hasColorVariance false-positive with monochrome test image
- mask-ux.spec.ts: rename test to match new rendering (no green overlay)
- playwright.config.ts: set baseURL when webServer is used so page.goto('/')
resolves correctly in local dev
Fixes: issue #55 mask preview
Replace green overlay rendering with cutout-on-checkerboard preview:
- Slab pixels show actual photo RGB with mask-based alpha
- Removed background area shows 10px checkerboard (224/192 gray)
- Knob debounce from a1d4a96 preserved unchanged
Update Playwright test to assert checkerboard + slab pixels
visible, not green overlay avgAlpha.