fix(internal/vfs): don't give archive/tar Sys data

Signed-off-by: Xe Iaso <[e-mail]>

internal/vfs/modtimefs.go

···
 	return "root", nil
 }
 
+func (fi modTimeFileInfo) Sys() any {
+	return nil
+}
+
 // modTimeDirEntry wraps fs.DirEntry to override Info().ModTime().
 type modTimeDirEntry struct {
 	fs.DirEntry