fix: use .default fallback for @babel/traverse CJS import

Vite's SSR transform wraps CJS module.exports as .default, so the
traverse function ends up at traverseModule.default. Use a simple
fallback pattern that works in both vite and native Node contexts.

Author: jdalton

test/unit/bundle-validation.test.mts

@@ -8,12 +8,14 @@ import path from 'node:path'
 import { fileURLToPath } from 'node:url'
 
 import { parse } from '@babel/parser'
-import _traverse from '@babel/traverse'
-
-// @babel/traverse CJS exports { default: fn } — resolve for both native and vite contexts
-const traverse = typeof _traverse === 'function' ? _traverse : _traverse.default
+import traverseModule from '@babel/traverse'
 import { describe, expect, it } from 'vitest'
 
+// @babel/traverse is CJS — vite wraps module.exports as .default
+const traverse = (
+  traverseModule as unknown as { default: typeof traverseModule }
+).default
+
 const __dirname = path.dirname(fileURLToPath(import.meta.url))
 const packagePath = path.resolve(__dirname, '../..')
 const distPath = path.join(packagePath, 'dist')