feat: add native binary compilation to releases

- Add Bun-based native binary compilation for macOS, Linux, and Windows
- Create build_binaries.js script to compile from bundle/gemini.js
- Update release workflow to build and include binaries in GitHub releases
- Add build:binaries npm script

Related to #3804

scripts/build_binaries.js

@@ -0,0 +1,78 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { execSync } from 'child_process';
+import fs from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const rootDir = path.resolve(__dirname, '..');
+
+const bundleJs = path.join(rootDir, 'bundle', 'gemini.js');
+const outputDir = path.join(rootDir, 'bundle', 'binaries');
+
+// Binary targets configuration
+const targets = [
+  { name: 'gemini-cli-darwin-x64', target: 'bun-darwin-x64' },
+  { name: 'gemini-cli-darwin-arm64', target: 'bun-darwin-arm64' },
+  { name: 'gemini-cli-linux-x64', target: 'bun-linux-x64' },
+  { name: 'gemini-cli-linux-arm64', target: 'bun-linux-arm64' },
+  { name: 'gemini-cli-windows-x64.exe', target: 'bun-windows-x64' },
+];
+
+// Check if bundle/gemini.js exists
+if (!fs.existsSync(bundleJs)) {
+  console.error('Error: bundle/gemini.js not found. Please run "npm run bundle" first.');
+  process.exit(1);
+}
+
+// Create output directory
+if (!fs.existsSync(outputDir)) {
+  fs.mkdirSync(outputDir, { recursive: true });
+  console.log(`Created directory: ${outputDir}`);
+}
+
+console.log('Building native binaries from bundle/gemini.js...\n');
+
+let successCount = 0;
+let failedTargets = [];
+
+for (const { name, target } of targets) {
+  const outputPath = path.join(outputDir, name);
+  console.log(`Building ${name}...`);
+  
+  try {
+    const command = `bun build --compile --target=${target} ${bundleJs} --outfile ${outputPath}`;
+    execSync(command, { stdio: 'pipe' });
+    
+    // Check if file was created
+    if (fs.existsSync(outputPath)) {
+      const stats = fs.statSync(outputPath);
+      const sizeMB = (stats.size / (1024 * 1024)).toFixed(1);
+      console.log(`  ✓ Built ${name} (${sizeMB} MB)`);
+      successCount++;
+    } else {
+      throw new Error('Binary file was not created');
+    }
+  } catch (error) {
+    console.error(`  ✗ Failed to build ${name}`);
+    console.error(`    ${error.message}`);
+    failedTargets.push(name);
+  }
+}
+
+console.log('\n' + '='.repeat(50));
+console.log(`Build complete: ${successCount}/${targets.length} binaries built successfully`);
+
+if (failedTargets.length > 0) {
+  console.log(`Failed targets: ${failedTargets.join(', ')}`);
+  console.log('\nNote: Cross-compilation may require Bun 1.1.0+ and might not work for all targets from all host platforms.');
+  console.log('In CI, all targets should build successfully on the appropriate runner.');
+}
+
+console.log(`\nBinaries saved to: ${outputDir}`);