Implement MusicManager fade-out in stopMusic() — was a stub

stopMusic(fadeMs) previously had (void)fadeMs with no fade logic.
Added fadingOut/fadeOutTimer/fadeOutDuration/fadeOutStartVolume state
and wired update() to interpolate volume to zero then stop playback.
Also clean up DuelProposedPacket comment (removed misleading TODO label).

include/audio/music_manager.hpp

@@ -52,6 +52,11 @@ private:
     float fadeInTimer = 0.0f;
     float fadeInDuration = 0.0f;
     float fadeInTargetVolume = 0.0f;
+    // Fade-out state (for stopMusic with fadeMs > 0)
+    bool fadingOut = false;
+    float fadeOutTimer = 0.0f;
+    float fadeOutDuration = 0.0f;
+    float fadeOutStartVolume = 0.0f;
 
     std::unordered_map<std::string, std::vector<uint8_t>> musicDataCache_;
 };

src/audio/music_manager.cpp

@@ -144,15 +144,24 @@ void MusicManager::playFilePath(const std::string& filePath, bool loop, float fa
 }
 
 void MusicManager::stopMusic(float fadeMs) {
-    (void)fadeMs;  // Fade not implemented yet
-    AudioEngine::instance().stopMusic();
-    playing = false;
+    if (!playing) return;
+
     fadingIn = false;
-    fadeInTimer = 0.0f;
-    fadeInDuration = 0.0f;
-    fadeInTargetVolume = 0.0f;
-    currentTrack.clear();
-    currentTrackIsFile = false;
+    crossfading = false;
+
+    if (fadeMs > 0.0f) {
+        // Begin fade-out; actual stop happens once volume reaches zero in update()
+        fadingOut = true;
+        fadeOutTimer = 0.0f;
+        fadeOutDuration = fadeMs / 1000.0f;
+        fadeOutStartVolume = effectiveMusicVolume();
+    } else {
+        AudioEngine::instance().stopMusic();
+        playing = false;
+        fadingOut = false;
+        currentTrack.clear();
+        currentTrackIsFile = false;
+    }
 }
 
 void MusicManager::setVolume(int volume) {
@@ -224,6 +233,22 @@ void MusicManager::update(float deltaTime) {
         playing = false;
     }
 
+    if (fadingOut) {
+        fadeOutTimer += deltaTime;
+        float t = std::clamp(1.0f - fadeOutTimer / std::max(fadeOutDuration, 0.001f), 0.0f, 1.0f);
+        AudioEngine::instance().setMusicVolume(fadeOutStartVolume * t);
+        if (t <= 0.0f) {
+            // Fade complete — stop playback and restore volume for next track
+            fadingOut = false;
+            AudioEngine::instance().stopMusic();
+            AudioEngine::instance().setMusicVolume(effectiveMusicVolume());
+            playing = false;
+            currentTrack.clear();
+            currentTrackIsFile = false;
+        }
+        return;  // Don't process other fade logic while fading out
+    }
+
     if (fadingIn) {
         fadeInTimer += deltaTime;
         float t = std::clamp(fadeInTimer / std::max(fadeInDuration, 0.001f), 0.0f, 1.0f);

src/game/world_packets.cpp

@@ -2131,9 +2131,8 @@ network::Packet RequestRaidInfoPacket::build() {
 // ============================================================
 
 network::Packet DuelProposedPacket::build(uint64_t targetGuid) {
-    // TODO: Duels are initiated via CMSG_CAST_SPELL with spell 7266,
-    // not a dedicated CMSG_DUEL_PROPOSED opcode (which doesn't exist in WoW).
-    // For now, build a cast spell packet targeting the opponent.
+    // Duels are initiated via CMSG_CAST_SPELL with spell 7266 (Duel) targeted at the opponent.
+    // There is no separate CMSG_DUEL_PROPOSED opcode in WoW.
     auto packet = CastSpellPacket::build(7266, targetGuid, 0);
     LOG_DEBUG("Built duel request (spell 7266) for target: 0x", std::hex, targetGuid, std::dec);
     return packet;