updating and refining plugin system refactor

MPV/LUA/main.lua

@@ -4105,6 +4105,9 @@ function M._apply_web_subtitle_load_defaults(reason)
     if target == '' or not _is_http_url(target) then
         return false
     end
+    if not _is_ytdlp_url(target) then
+        return false
+    end
 
     M._prepare_ytdl_format_for_web_load(target, reason or 'on-load')
 
@@ -4250,6 +4253,9 @@ function M._ensure_current_subtitles_visible(reason)
     if (not current or current == '') and (path == '' or not _is_http_url(path)) then
         return false
     end
+    if (not current or current == '') and (path == '' or not _is_ytdlp_url(path)) then
+        return false
+    end
 
     local track_id, source, already_selected = M._find_subtitle_track_candidate()
     if not track_id then