voice: add global playback speed control for audio and voice

web/src/store/audioPlayerStore.ts

@@ -10,6 +10,7 @@ interface AudioPlayerState {
   audioEl: HTMLAudioElement | null;
   isPlaying: boolean;
   volume: number;
+  playbackRate: number;
   duration: number;
   position: number;
   playTrack: (track: ActiveTrack) => Promise<void>;
@@ -17,11 +18,25 @@ interface AudioPlayerState {
   seekTo: (seconds: number) => void;
   seekBy: (secondsDelta: number) => void;
   setVolume: (volume: number) => void;
+  setPlaybackRate: (rate: number) => void;
+  cyclePlaybackRate: () => void;
   stop: () => void;
 }
 
 let globalAudioEl: HTMLAudioElement | null = null;
 let isBound = false;
+const PLAYBACK_RATE_KEY = "bm_audio_playback_rate";
+
+function getInitialPlaybackRate(): number {
+  if (typeof window === "undefined") {
+    return 1;
+  }
+  const raw = Number(window.localStorage.getItem(PLAYBACK_RATE_KEY) || "1");
+  if (raw === 1 || raw === 1.5 || raw === 2) {
+    return raw;
+  }
+  return 1;
+}
 
 function ensureAudio(): HTMLAudioElement {
   if (globalAudioEl) {
@@ -37,6 +52,7 @@ export const useAudioPlayerStore = create<AudioPlayerState>((set, get) => ({
   audioEl: ensureAudio(),
   isPlaying: false,
   volume: 1,
+  playbackRate: getInitialPlaybackRate(),
   duration: 0,
   position: 0,
   playTrack: async (track) => {
@@ -63,6 +79,7 @@ export const useAudioPlayerStore = create<AudioPlayerState>((set, get) => ({
       set({ track });
     }
     audio.volume = get().volume;
+    audio.playbackRate = get().playbackRate;
     try {
       await audio.play();
       set({ isPlaying: true, audioEl: audio });
@@ -111,6 +128,20 @@ export const useAudioPlayerStore = create<AudioPlayerState>((set, get) => ({
     audio.volume = normalized;
     set({ volume: normalized });
   },
+  setPlaybackRate: (rate) => {
+    const normalized = rate === 2 ? 2 : rate === 1.5 ? 1.5 : 1;
+    const audio = ensureAudio();
+    audio.playbackRate = normalized;
+    if (typeof window !== "undefined") {
+      window.localStorage.setItem(PLAYBACK_RATE_KEY, String(normalized));
+    }
+    set({ playbackRate: normalized });
+  },
+  cyclePlaybackRate: () => {
+    const current = get().playbackRate;
+    const next = current === 1 ? 1.5 : current === 1.5 ? 2 : 1;
+    get().setPlaybackRate(next);
+  },
   stop: () => {
     const audio = ensureAudio();
     if (audio) {