fix(tests): Add shebangs, set -e, and comprehensive checks to Ubuntu test scripts

- Rewrite test_latest.sh with real tests for NVM, Node.js, pnpm, Bun, Deno, and version switching
- Add #!/bin/bash shebang and set -e to test_stable.sh and test_npmci.sh

test/test_latest.sh

@@ -1 +1,32 @@
-echo "this runs within latest container!";
+#!/bin/bash
+set -e
+
+echo "Testing latest image..."
+
+# Test NVM
+echo "Testing NVM..."
+nvm --version
+
+# Test Node.js
+echo "Testing Node.js..."
+node --version
+
+# Test pnpm
+echo "Testing pnpm..."
+pnpm --version
+
+# Test Bun
+echo "Testing Bun..."
+bun --version
+
+# Test Deno
+echo "Testing Deno..."
+deno --version
+
+# Test NVM version switching
+echo "Testing NVM version switching..."
+nvm install 22
+nvm use 22
+node --version | grep v22
+
+echo "latest tests passed!"