Document LPIPS VGG cache file

README.md

@@ -20,6 +20,7 @@ Pwavevelocity.mat
 marmousi/marmousi_256_train.npz
 overthrust/Overthrust_trueimp.mat
 prepare_marmousi_256_train.py
+vgg.pth
 ```
 
 `Pwavevelocity.mat` is the official Marmousi velocity model file used by the default Stage 1 VQGAN multi-scale training config and the experimental Diffusers VQGAN trainer.
@@ -30,6 +31,8 @@ prepare_marmousi_256_train.py
 
 `prepare_marmousi_256_train.py` is a minimal data preparation script documenting the Marmousi-derived training data recipe. It expects `Pwavevelocity.mat` and writes the training `.npz` file.
 
+`vgg.pth` is the LPIPS linear-weight checkpoint used by the VQGAN perceptual loss. The training code copies it to `tmp/vgg.pth` automatically when present in this data directory.
+
 Example `.env` entries for the code repository:
 
 ```bash