* perplexity: add signal-driven hot-swap mode for persistent KLD/PPL benchmarking
llama-perplexity can now stay resident and be driven through control/status files (reload/compute/exit): it reloads only the tensors that changed on disk and recomputes PPL/KLD without ever reloading the full model. File-based signalling works on Windows, macOS and Linux. The reload returning-to-original path now refreshes tensor data from disk instead of
reattaching stale weights.
* Not Cygwin specific