ComfyUI may register diffusion_models as an alias of unet in
folder_paths, so get_folder_paths("diffusion_models") returns the
unet directory. This caused downloads to be saved in models/unet
even when the user selected diffusion_models.
Now get_model_dir prefers the physical folder
models/<normalized_type> when it exists, and verifies that the path
returned by folder_paths actually matches the requested type name
before using it. If folder_paths returns an alias, a dedicated
folder is created under models/ instead.
huchukato
e90f2c104c