ci: install host GL runtime libs for the AppImage

AppRun refuses to start without libOpenGL.so.0 (bare runners lack
libopengl0/libglu1-mesa; desktops have them, which is why local testing
passed).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XqSEqBGY9RYF96J8aCgxGy

.github/workflows/parity.yml

@@ -93,7 +93,8 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get install -y --no-install-recommends \
-            xvfb xdotool imagemagick openbox mesa-utils
+            xvfb xdotool imagemagick openbox mesa-utils \
+            libopengl0 libglu1-mesa libgl1 libegl1
 
       - name: Run the parity harness
         id: run