Fix GitHub Actions: generate Solana keypair for tests

The tests require a Solana keypair at ~/.config/solana/id.json
which doesn't exist in GitHub Actions environment. Generate one
before running tests.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: mikemaccana

.github/workflows/test.yml

@@ -35,6 +35,11 @@ jobs:
 
       - run: solana --version
 
+      - name: Generate Solana keypair
+        run: |
+          mkdir -p ~/.config/solana
+          solana-keygen new --no-bip39-passphrase --silent --outfile ~/.config/solana/id.json
+
       - run: npm i
 
       - run: npm test