Handle mpv reload buffering as same media

- Keep overlay alive across same-media mpv reloads
- Avoid rearming startup gate and repeating AniSkip lookups
- Add regression coverage for reload/end-file/file-loaded sequence

plugin/subminer/state.lua

@@ -33,6 +33,8 @@ function M.new()
 		auto_play_ready_timeout = nil,
 		auto_play_ready_osd_timer = nil,
 		suppress_ready_overlay_restore = false,
+		current_media_identity = nil,
+		pending_reload_media_identity = nil,
 		session_binding_generation = 0,
 		session_binding_names = {},
 		session_numeric_binding_names = {},