Cache-Backed Recovery

ICacheQ is the public runtime surface used when a payload-aware graph must be persisted before in-memory execution.

1. The payload graph is dehydrated into the cache.
2. ResumePolling() enables the leasing loop.
3. CacheQ leases pending roots when the wrapped IParallelQ has capacity.
4. The leased root is hydrated and enqueued into the wrapped queue.