docs: provenance — mixed authorship, GPAI status

card: correct EGSet12 to measured 12-track F1 0.59 (was a single-track 0.77)

card: document both variants + per-variant CQT normalization

add GuitarProFX-augmented variant (electric-robust, EGSet12 F1 ~0.77)

TabCNN ONNX + CQT filterbank + model card (trained on GuitarSet CC BY 4.0)

initial commit