Give the version-layout fixture a module type

The fixture simulates a real package root but omitted `"type": "module"`,
so Node 24 and 26 emitted MODULE_TYPELESS_PACKAGE_JSON on stderr and the
test's empty-stderr assertion failed. Node 22 does not warn, and a local
`--no-warnings` in NODE_OPTIONS hid it outside CI.

Co-Authored-By: Claude (Opus 5) <noreply@anthropic.com>

Author: silverwind

index.test.ts

@@ -466,7 +466,7 @@ test("version resolves the source and built package layouts", async ({expect = g
   const source = await readFile(sourceScript, "utf8");
   await Promise.all([
     writeFile(join(parentDir, "package.json"), JSON.stringify({version: "wrong"})),
-    writeFile(join(sourceDir, "package.json"), JSON.stringify({version: "1.2.3"})),
+    writeFile(join(sourceDir, "package.json"), JSON.stringify({version: "1.2.3", type: "module"})),
     writeFile(join(sourceDir, "index.ts"), source),
     writeFile(join(distDir, "index.ts"), source),
   ]);