test: run unit tests in series to remove race conditions

Author: gingerbenw

vitest.config.ts

@@ -0,0 +1,8 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    // Run tests in sequence to avoid race conditions with shared fixture directories
+    fileParallelism: false
+  }
+})