Try to nix run demo directly on CI

Author: vrom911

.github/workflows/demo-test.yaml

@@ -27,5 +27,9 @@ jobs:
 
       - name: Check demo test
         run: |
-          nix develop .#demo -c bash -c "cd demo && ./test.sh"
+          cd demo
+          nix run .#demo -- -D
+          sleep 30  # Give time for startup
+          cat devnet/alice-logs.txt | grep "APIServerStarted" || exit 1
+          nix run .#demo -- down