GPU spam guard (serialize + button lock), live progress tickers, describe-first layout, real-machine bindings, chart fix for custom VRAM

Load speed predictor via xgboost native format

Speed predictions now come from a model trained on 6.6k real measurements (17.5% median error on unseen hardware), physics formula beyond its measured range

Speed predictions with receipts: bandwidth roofline, real-runs chart, honest provenance