feat: CC lane dropdown with Velocity, Sustain, Modulation, Pitch Bend, Pan

Replaced flex div with velocity/pan buttons with a
<select> dropdown containing 5 CC type options.
Default: Velocity. Button toggle shows short label.

app/static/js/app.jsx

@@ -5957,16 +5957,14 @@ const beatSec = 60.0 / (parseInt(bpm) || 120);
     }), React.createElement("span", { className: "text-zinc-500" }, "-"), React.createElement("input", {
       type: "number", value: aiBarEnd, onChange: e => setAiBarEnd(parseInt(e.target.value) || 1),
       className: "w-8 bg-zinc-900 border border-zinc-700 text-zinc-200 rounded px-1 py-0.5 text-xs text-center"
-    }), React.createElement("span", { className: "text-zinc-500" }, "bar")), React.createElement("div", {
-      className: "flex bg-zinc-800 p-0.5 rounded border border-zinc-700 text-xs"
-    }, ['velocity', 'pan'].map(mode => React.createElement("button", {
-      key: mode,
-      onClick: () => setCcMode(mode),
-      className: `px-2.5 py-1 rounded capitalize ${ccMode === mode ? 'bg-purple-900/60 text-purple-300 font-bold border border-purple-700' : 'text-zinc-400 hover:text-zinc-200'}`
-    }, mode)))), React.createElement("button", {
+    }), React.createElement("span", { className: "text-zinc-500" }, "bar")), React.createElement("select", {
+      value: ccMode,
+      onChange: e => setCcMode(e.target.value),
+      className: "bg-zinc-800 text-zinc-200 border border-zinc-700 rounded px-1.5 py-1 text-xs capitalize cursor-pointer"
+    }, React.createElement("option", { value: "velocity" }, "Velocity"), React.createElement("option", { value: "sustain" }, "Sustain"), React.createElement("option", { value: "modulation" }, "Modulation"), React.createElement("option", { value: "pitch_bend" }, "Pitch Bend"), React.createElement("option", { value: "pan" }, "Pan"))), React.createElement("button", {
       onClick: () => setShowCC(!showCC),
       className: `px-2 py-1 rounded text-xs ${showCC ? 'bg-purple-900/60 text-purple-300 border border-purple-700' : 'text-zinc-500 hover:text-zinc-300'}`
-    }, ccMode === 'pan' ? 'Pan' : 'Vel'), React.createElement("button", {
+    }, ccMode === 'velocity' ? 'Vel' : ccMode === 'sustain' ? 'Sus' : ccMode === 'modulation' ? 'Mod' : ccMode === 'pitch_bend' ? 'Bend' : ccMode === 'pan' ? 'Pan' : 'CC'), React.createElement("button", {
       onClick: function() { setSessionSyncMode(function(p) { return !p; }); },
       className: function() {
         var base = 'px-2 py-1 rounded text-xs ';