chore: prepare v1.15.0 release and exclude generated test copies

vitest.config.ts

@@ -0,0 +1,9 @@
+import { configDefaults, defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    // TypeScript compiles test files into dist. Test the source once, even
+    // when an older build is present, rather than collecting stale copies.
+    exclude: [...configDefaults.exclude, "dist/**", "web/dist/**"],
+  },
+});