fix: keep seek target visible until acknowledged and make volume thumb opaque

Sources/Core/player.cpp

@@ -137,6 +137,7 @@ struct Player {
             state.status = PLAYER_OPENING;
             state.revision = revision;
         }
+        if (commands.back().action == Action::Seek) state.seek_pending = true;
         wake.notify_one();
         return true;
     }
@@ -179,6 +180,10 @@ struct Player {
         state.duration = duration;
         state.has_audio = tracks[0].codec != nullptr;
         state.has_video = tracks[1].codec != nullptr;
+        // The worker publishes only outside seek execution; retain pending for later queued seeks.
+        state.seek_pending = std::any_of(commands.begin(), commands.end(), [this](const Command &command) {
+            return command.action == Action::Seek && command.epoch == activeEpoch;
+        });
         state.video_aspect_ratio = 0;
         if (const auto *video = tracks[1].codec; video && video->width > 0 && video->height > 0) {
             const auto aspect = av_guess_sample_aspect_ratio(format, format->streams[tracks[1].index], nullptr);

Sources/Core/player.h

@@ -17,6 +17,8 @@ typedef struct PlayerState {
     double duration;
     bool has_audio;
     bool has_video;
+    // True from accepted seek until all queued seeks on this timeline finish.
+    bool seek_pending;
     // Display width / height, including sample aspect ratio; zero without video.
     double video_aspect_ratio;
     uint64_t revision;