fix: move Chromium download to Docker build phase

- Download Chromium from Google snapshots during Docker build (network works there)
- Chroot hook now only verifies and installs runtime dependencies
- Remove generated files from repo (OVMF_VARS.fd, qemu.pid, screenshots)
- Update isotest scripts to use .nogit/ directory structure
- Chromium kiosk verified working with Sway compositor

isobuild/config/autoinstall/user-data

@@ -66,10 +66,7 @@ autoinstall:
     # Enable eco-daemon service
     - curtin in-target -- systemctl enable eco-daemon
 
-    # Install Google Chrome
-    - curtin in-target -- wget -q -O /tmp/chrome.deb https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
-    - curtin in-target -- apt-get install -y /tmp/chrome.deb
-    - curtin in-target -- rm /tmp/chrome.deb
+    # Chromium is already installed in the ISO via live-build hook
 
   # Reboot after installation
   shutdown: reboot