fix: prevent metronome from auto-starting when opening controls

The metronome was starting immediately when opening the controls popup,
which is incorrect behavior. Users should explicitly click the Apply
button to start the metronome.

Changes:
- Removed SessionOpenMetronome() call from handleMetronomeSelected
- Metronome controls now show without starting audio
- Apply button calls SessionSetMetronome() to start/update metronome
- Subsequent opens still don't auto-start

Behavior:
- Open metronome → Controls appear, no audio
- Click Apply → Metronome starts with chosen settings
- Close & reopen → Controls appear, no auto-start

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

jam-ui/src/components/client/JKSessionScreen.js

@@ -1025,28 +1025,26 @@ const JKSessionScreen = () => {
       // Stop any current playback first (like legacy MixerStore)
       await jamClient.SessionStopPlay();
 
-      // Open the metronome with default settings
+      // Default metronome settings for the controls
       const bpm = 120;
-      const sound = "Beep";
+      const sound = 2; // Beep
       const meter = 1;
-      const mode = 0;
+      const cricket = false;
 
-      console.log(`Opening metronome with bpm: ${bpm}, sound: ${sound}, meter: ${meter}, mode: ${mode}`);
+      console.log(`Opening metronome controls with default settings: bpm=${bpm}, sound=${sound}, meter=${meter}`);
 
       // Inform server about metronome opening (like legacy SessionStore)
       await openMetronome({ id: currentSession.id });
 
-      // Start the metronome audio (backend will handle GUI via callback)
-      const result = await jamClient.SessionOpenMetronome(bpm, sound, meter, mode);
-
       // Update local metronome state to show popup immediately
+      // NOTE: We don't start the metronome audio here - user must click Apply in popup
       if (updateMetronomeState) {
         updateMetronomeState({
           isOpen: true,
           bpm: bpm,
-          sound: 2, // Beep
+          sound: sound,
           meter: meter,
-          cricket: mode === 1
+          cricket: cricket
         });
       }