Each folder in the listing now carries its effective display filter:
the registered extension set, or the global supported_pt_extensions for
match-all folders (registered with an empty set, e.g. LLM). Resolved per
request so runtime registrations by custom nodes are reflected.
Lets the asset-backed model sidebar filter match-all folder contents
(hiding README/config noise) without hardcoding the global set client
side, while registered folders stay governed by the scanner's
extension-filtered model_type tags.
