feat: Add GitHub deployment artifacts (homebrew, npm) (gt-ufep6)

- Add .goreleaser.yml for multi-platform binary releases
- Add npm-package/ with postinstall binary download
- Add release.yml workflow for GoReleaser + npm publish + Homebrew tap

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

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

npm-package/scripts/test.js

@@ -0,0 +1,53 @@
+#!/usr/bin/env node
+
+const { execSync } = require('child_process');
+const path = require('path');
+const fs = require('fs');
+const os = require('os');
+
+console.log('Running gt npm package tests...\n');
+
+let passed = 0;
+let failed = 0;
+
+function test(name, fn) {
+  try {
+    fn();
+    console.log(`[PASS] ${name}`);
+    passed++;
+  } catch (err) {
+    console.log(`[FAIL] ${name}: ${err.message}`);
+    failed++;
+  }
+}
+
+// Test 1: Check binary exists
+test('Binary exists in bin directory', () => {
+  const binaryName = os.platform() === 'win32' ? 'gt.exe' : 'gt';
+  const binaryPath = path.join(__dirname, '..', 'bin', binaryName);
+  if (!fs.existsSync(binaryPath)) {
+    throw new Error(`Binary not found at ${binaryPath}`);
+  }
+});
+
+// Test 2: Binary is executable (version check)
+test('Binary executes and returns version', () => {
+  const binaryName = os.platform() === 'win32' ? 'gt.exe' : 'gt';
+  const binaryPath = path.join(__dirname, '..', 'bin', binaryName);
+  const output = execSync(`"${binaryPath}" version`, { encoding: 'utf8' });
+  if (!output.includes('gt version')) {
+    throw new Error(`Unexpected version output: ${output}`);
+  }
+});
+
+// Test 3: Wrapper script exists
+test('Wrapper script (gt.js) exists', () => {
+  const wrapperPath = path.join(__dirname, '..', 'bin', 'gt.js');
+  if (!fs.existsSync(wrapperPath)) {
+    throw new Error(`Wrapper not found at ${wrapperPath}`);
+  }
+});
+
+// Summary
+console.log(`\n${passed} passed, ${failed} failed`);
+process.exit(failed > 0 ? 1 : 0);