Function asset_file_name 

pub fn asset_file_name(plugin_id: &str, asset_id: &str, ext: &str) -> String

Sidecar filename for one of plugin plugin_id’s image assets. Both plugin_id (reverse-DNS) and asset_id ([a-z0-9._-]) are validated at install, so the result is a single safe filename component — no separators, no traversal. Recorded in the registry so uninstall can remove exactly it.