Tests: document fresh import helper

test/helpers/import-fresh.ts

@@ -2,5 +2,7 @@ export async function importFreshModule<TModule>(
   from: string,
   specifier: string,
 ): Promise<TModule> {
+  // Vitest keys module instances by the full URL string, including the query
+  // suffix. These tests rely on that behavior to emulate code-split chunks.
   return (await import(/* @vite-ignore */ new URL(specifier, from).href)) as TModule;
 }