Add type smoke test for public entry point exports

Imports PageData at runtime and verifies it is a class. TypeScript also
checks the @typedef imports for PageInfo, TemplateInfo, LayoutFunctionParams,
GlobalDataFunctionParams, PageFunctionParams, and TemplateFunctionParams at
compile time via npm run test:tsc.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: bcomnes

test-cases/type-exports/index.test.js

@@ -0,0 +1,20 @@
+// @ts-check
+import { test } from 'node:test'
+import assert from 'node:assert'
+import { PageData } from '../../index.js'
+
+/**
+ * Smoke test that all public types are importable from the package entry point.
+ * The @typedef imports below are verified by TypeScript at compile time via `npm run test:tsc`.
+ *
+ * @typedef {import('../../index.js').PageInfo} PageInfo
+ * @typedef {import('../../index.js').TemplateInfo} TemplateInfo
+ * @typedef {import('../../index.js').LayoutFunctionParams} LayoutFunctionParams
+ * @typedef {import('../../index.js').GlobalDataFunctionParams} GlobalDataFunctionParams
+ * @typedef {import('../../index.js').PageFunctionParams} PageFunctionParams
+ * @typedef {import('../../index.js').TemplateFunctionParams} TemplateFunctionParams
+ */
+
+test('PageData is importable from the package entry point', () => {
+  assert.strictEqual(typeof PageData, 'function', 'PageData is a class')
+})