fix(agents): honor explicit rate-limit cooldown probes in fallback runs

src/test-utils/model-fallback.mock.ts

@@ -1,7 +1,11 @@
 export async function runWithModelFallback(params: {
   provider: string;
   model: string;
-  run: (provider: string, model: string) => Promise<unknown>;
+  run: (
+    provider: string,
+    model: string,
+    options?: { allowRateLimitCooldownProbe?: boolean },
+  ) => Promise<unknown>;
 }) {
   return {
     result: await params.run(params.provider, params.model),