fix: ghost border, track buttons clickable, per-track instrument silent

- Remove dashed border from ghost notes (fill-only at 25% opacity)
- Track column: replaced div overlay with natural flex child; use
  <button> elements with border-l-2 indicator; removed pointer-events
- Ghost playback: skip layers with no instrument assigned (silent)
  instead of playing with default piano

app/static/js/app.jsx

@@ -4912,10 +4912,6 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, activeTracks, onClos
           var w = note.duration_beats * pixelsPerBeat;
           var h = NoteHeight - 1;
           ctx.fillRect(x, y, w, h);
-          ctx.setLineDash([2, 2]);
-          ctx.lineWidth = 1;
-          ctx.strokeRect(x, y, w, h);
-          ctx.setLineDash([]);
         });
         ctx.restore();
       });
@@ -6127,11 +6123,9 @@ const beatSec = 60.0 / (parseInt(bpm) || 120);
     /* 3. MAIN PIANO ROLL GRID (KEYBOARD + TRACK COL + CANVAS) */
     React.createElement("div", {
       className: "flex-1 flex overflow-hidden min-h-0 relative"
-    }, /* Track column overlay — always visible */ React.createElement("div", {
+    }, /* Track column */ React.createElement("div", {
-      className: "absolute left-0 top-0 w-[120px] bg-[#16161a] border-r border-zinc-800 z-10 flex flex-col overflow-hidden pointer-events-none",
+      className: "w-[120px] bg-[#16161a] border-r border-zinc-800 shrink-0 flex flex-col z-10",
       style: { height: KeybedPixelHeight + 'px' }
-    }, React.createElement("div", {
-      className: "pointer-events-auto flex flex-col"
     }, (allMidiItems.length > 0 ? function() {
       var seenTracks = {};
       var els = [];
@@ -6141,7 +6135,7 @@ const beatSec = 60.0 / (parseInt(bpm) || 120);
         var track = (activeTracks || []).find(function(t) { return t.id === m._trackId; });
         var isActive = m._trackId === st.trackId && m.id === st.target_id;
         var isPlayOn = activePlayTrackIds === null || activePlayTrackIds.has(m._trackId);
-        els.push(React.createElement("div", {
+        els.push(React.createElement("button", {
           key: m._trackId,
           onClick: function() {
             if (isActive) return;
@@ -6152,19 +6146,17 @@ const beatSec = 60.0 / (parseInt(bpm) || 120);
               return s.size === 0 ? null : s;
             });
           },
-          className: "flex items-center justify-center h-[18px] border-b border-zinc-900 cursor-pointer select-none " + (isActive ? 'bg-yellow-600 text-black font-bold' : (isPlayOn ? 'bg-purple-700 text-white font-semibold' : 'bg-zinc-800 text-zinc-500 hover:bg-zinc-700'))
+          className: "w-full flex items-center justify-center h-[18px] border-b border-zinc-900 cursor-pointer outline-none " + (isActive ? 'bg-yellow-600 text-black font-bold border-l-2 border-l-yellow-300' : (isPlayOn ? 'bg-purple-700 text-white font-semibold border-l-2 border-l-purple-400' : 'bg-zinc-800 text-zinc-500 hover:bg-zinc-700 border-l-2 border-l-transparent'))
         }, React.createElement("span", {
           className: "text-[12px] font-sans truncate px-1",
           title: track ? track.name : m._trackName
         }, track ? track.name : m._trackName)));
       });
       return els;
-    }() : null))), React.createElement("div", {
+    }() : null)), React.createElement("div", {
-      className: "w-[120px] shrink-0"
+      className: "w-[60px] shrink-0 flex flex-col border-r border-zinc-900 overflow-y-auto",
-    }), React.createElement("div", {
       ref: keybedRef,
       onScroll: handleKeybedScroll,
-      className: "w-[60px] overflow-y-auto flex flex-col border-r border-zinc-900 shrink-0",
       style: {
         scrollbarWidth: 'none',
         msOverflowStyle: 'none'
@@ -10421,6 +10413,7 @@ const App = () => {
       var ghostTrack = allTracks.find(function(t) { return t.id === layer.trackId; });
       var ghostProg = layer.instrumentProgram !== undefined ? layer.instrumentProgram : (ghostTrack ? ghostTrack.instrumentProgram : undefined);
       var ghostSynth = layer.synthEngine || (ghostTrack ? ghostTrack.synth_engine : undefined);
+      if (ghostProg === undefined && !ghostSynth) return; // skip tracks with no instrument
       var ghostDest = getOrCreateTrackNode(ghostTrack, context);
       var ghostCh = 0;
       for (var i = 0; i < allTracks.length; i++) { if (allTracks[i].id === layer.trackId) { ghostCh = i >= 9 ? i + 1 : i; if (ghostCh >= 16) ghostCh = 0; break; } }