Add Docker diagnostics to GitHub Actions

Verify Docker is running before tests since Arcium MPC nodes require Docker.
This will help diagnose the localnet timeout issue.

Author: mikemaccana

.github/workflows/test.yml

@@ -67,6 +67,13 @@ jobs:
           mkdir -p ~/.config/solana
           solana-keygen new --no-bip39-passphrase --silent --outfile ~/.config/solana/id.json
 
+      # Verify Docker is running and can pull images
+      # Arcium requires Docker to run MPC nodes during tests
+      - name: Verify Docker
+        run: |
+          docker info
+          docker ps
+
       - run: npm i
 
       - run: npm test