fix(deps): externalize tree-sitter (#840)

Submitting without approval to fix broken deployment on main. But also, we should lock this down.

esbuild.config.js

@@ -0,0 +1,29 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import esbuild from 'esbuild';
+
+esbuild
+  .build({
+    entryPoints: ['packages/cli/index.ts'],
+    bundle: true,
+    outfile: 'bundle/gemini.js',
+    platform: 'node',
+    format: 'esm',
+    banner: {
+      js: `import { createRequire } from 'module'; const require = createRequire(import.meta.url); globalThis.__filename = require('url').fileURLToPath(import.meta.url); globalThis.__dirname = require('path').dirname(globalThis.__filename);`,
+    },
+    external: [
+      'tree-sitter',
+      'tree-sitter-c-sharp',
+      'tree-sitter-go',
+      'tree-sitter-java',
+      'tree-sitter-python',
+      'tree-sitter-rust',
+      'tree-sitter-typescript',
+    ],
+  })
+  .catch(() => process.exit(1));