Fix double metronome click in single-note modes

useGameLogic's own scheduler and the footer widget's scheduler both
played audible clicks while rhythm.active — assist->learn-notes switch
made the second one mount. Now the widget is the single click source in
non-zen modes; useGameLogic's scheduler is a silent tick source for
auto-advance (full sound only in zen mode, where the widget isn't
rendered). Also: widget honors Timer mode (60/seconds) like the trainer,
and useMetronome skips audio nodes at volume 0.

src/components/MetronomeWidget.tsx

@@ -65,8 +65,12 @@ export const MetronomeWidget: React.FC<MetronomeWidgetProps> = ({
     // Free/plain: the widget's own scheduler runs whenever armed.
     const running = isSync ? runActive : armed;
 
+    // Timer mode = one beat per N seconds: effective BPM 60/seconds so
+    // clicks and pendulum match the trainer's auto-advance cadence.
+    const effectiveBpm = rhythm.mode === 'bpm' ? rhythm.bpm : 60 / Math.max(1, rhythm.seconds);
+
     const { restart } = useMetronome({
-        bpm: rhythm.bpm,
+        bpm: effectiveBpm,
         volume: rhythm.sound ? rhythm.volume : 0,
         playing: running && !isSync,
         onTick: handleTick,
@@ -82,7 +86,7 @@ export const MetronomeWidget: React.FC<MetronomeWidgetProps> = ({
         });
     }, [isSync, runActive]);
 
-    const beatMs = 60000 / Math.max(1, rhythm.bpm);
+    const beatMs = 60000 / Math.max(1, effectiveBpm);
 
     return (
         <div style={{ display: 'flex', flexDirection: 'column', gap: '8px' }}>

src/hooks/useGameLogic.ts

@@ -85,7 +85,11 @@ export const useGameLogic = (
 
     const { restart: restartMetronome } = useMetronome({
         bpm: effectiveBpm,
-        volume: settings.rhythm.sound ? settings.rhythm.volume : 0,
+        // Audible clicks come from the shared footer widget (Controls) in
+        // non-zen single-note modes — this scheduler is only the tick source
+        // for auto-advance. Sounding it here too doubles every beat. In zen
+        // mode the widget isn't rendered, so this scheduler IS the click.
+        volume: settings.zenMode && settings.rhythm.sound ? settings.rhythm.volume : 0,
         playing: settings.rhythm.active,
         onTick: handleTick
     });

src/hooks/useMetronome.ts

@@ -34,6 +34,8 @@ export function useMetronome({ bpm, volume, playing, onTick }: MetronomeOptions)
 
     const playClick = useCallback((time: number) => {
         if (!audioContext.current) return;
+        onTickRef.current(currentBeat.current);
+        if (volume <= 0) return; // silent tick source — no audio nodes needed
 
         const osc = audioContext.current.createOscillator();
         const gainNode = audioContext.current.createGain();