Keep make test from collecting tests in nested checkouts (closes #25)

vitest does not read .gitignore when finding tests, so a checkout nested
under .claude/ had its whole test/ tree run as part of this suite.
vitest.config.ts adds .claude/** to vitest's default excludes. The new
packaging test plants a nested checkout in a temp directory and fails if
vitest, run with this config, would collect it.

Model: opus-5-5

vitest.config.ts

@@ -0,0 +1,10 @@
+import { configDefaults, defineConfig } from "vitest/config";
+
+// vitest does not read .gitignore when looking for tests. A checkout nested
+// under .claude/ has its own test/ tree, and without this exclude the suite
+// runs once per nested checkout and still reports success.
+export default defineConfig({
+    test: {
+        exclude: [...configDefaults.exclude, ".claude/**"],
+    },
+});