Pi: fix kiosk WebGL2 (hardware V3D via ANGLE) + robust kiosk launch

- Drop --use-gl=egl (disabled the GPU on Chromium 149) and let Chromium pick the
  default ANGLE/GLES backend with --ignore-gpu-blocklist -> hardware WebGL2.
- Launch kiosk via 'cage -- bash kiosk.sh' so a non-executable bit after rsync
  no longer breaks startup.
- output.js reports gpuInfo (webgl2 + renderer) on load for remote diagnostics.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/kiosk.sh

@@ -8,5 +8,6 @@ exec "$BIN" \
   --disable-translate --disable-features=Translate \
   --check-for-update-interval=31536000 \
   --overscroll-history-navigation=0 \
-  --ozone-platform=wayland --use-gl=egl \
-  "$URL"
+  --ozone-platform=wayland \
+  --ignore-gpu-blocklist \
+  "$URL" >/tmp/chromium-kiosk.log 2>&1