CI: fix debian build test - use pip for pymavlink

python3-pymavlink and python3-pynmea2 are not available as apt packages
on Ubuntu, install via pip instead.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: tridge

.github/workflows/debian_build.yml

@@ -42,13 +42,18 @@ jobs:
 
       - name: Test package installation
         run: |
-          sudo apt-get install -y python3-pymavlink python3-pynmea2
+          # Install pip dependencies (pymavlink/pynmea2 not available as apt packages)
+          pip3 install pymavlink pynmeagps
+          # Install the built package, resolving any apt dependencies
           sudo dpkg -i ../python3-mavproxy*.deb || sudo apt-get -f install -y
           mavproxy.py --version || echo "Version check completed"
 
+      - name: Copy package to workspace
+        run: cp ../*.deb .
+
       - name: Archive Debian package
         uses: actions/upload-artifact@v4
         with:
           name: debian-package
-          path: ../*.deb
+          path: "*.deb"
           retention-days: 7