Delete smoke KV entries directly

Delete each smoke harness KV entry as it is listed instead of collecting
keys first.  The harness still clears the full dedicated MemoryKvStore so
/_test/reset remains a clean federation-state reset.

Resolves review comment:
#750 (comment)

Assisted-by: Codex:gpt-5.5

Author: dahlia

test/smoke/harness/federation.ts

@@ -17,11 +17,9 @@ const federation = createFederation<void>({
 });
 
 export async function resetFederationTestState(): Promise<void> {
-  const keys = [];
   for await (const entry of kv.list()) {
-    keys.push(entry.key);
+    await kv.delete(entry.key);
   }
-  await Promise.all(keys.map((key) => kv.delete(key)));
 }
 
 federation