refactor: simplify piano roll zoom - use CSS clip instead of manual grid extension

app/static/js/app.jsx

@@ -4433,9 +4433,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
   const rollBeatsRef = React.useRef(rollBeats);
   rollBeatsRef.current = rollBeats;
   const totalBeats = Math.max(rollBeats, noteMaxBeat + 16, 64); // at least 64 beats (16 bars) for scrolling
-  const [gridViewWidth, setGridViewWidth] = React.useState(800);
   const drawWidth = totalBeats * pixelsPerBeat;
-  const cssWidth = Math.max(drawWidth, gridViewWidth);
 
   const [notes, setNotes] = React.useState(st.notes || []);
   const [selectedNoteIds, setSelectedNoteIds] = React.useState([]);
@@ -4573,26 +4571,13 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     };
   }, [notes, st.currentTime, pixelsPerBeat, st.id, totalBeats, bpm]);
 
-  // Track grid container width for zoom fill
-  React.useEffect(() => {
-    const el = gridScrollRef.current;
-    if (!el) return;
-    const ro = new ResizeObserver(entries => {
-      for (const entry of entries) setGridViewWidth(entry.contentRect.width);
-    });
-    ro.observe(el);
-    setGridViewWidth(el.clientWidth);
-    return () => ro.disconnect();
-  }, []);
-
-  React.useEffect(() => {
+    React.useEffect(() => {
     const canvas = canvasRef.current;
     if (!canvas) return;
     const ctx = canvas.getContext('2d');
     const dpr = window.devicePixelRatio || 1;
     const h = 128 * NoteHeight;
-    const canvasW = Math.max(drawWidth, gridViewWidth);
-    canvas.width = canvasW * dpr;
+    canvas.width = drawWidth * dpr;
     canvas.height = h * dpr;
     ctx.scale(dpr, dpr);
 
@@ -4620,9 +4605,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     else if (snapVal === '1/16') snapBeats = 0.25;
     else if (snapVal === '1/32') snapBeats = 0.125;
 
-    const maxBeatPx = drawWidth;
-    const gridEndBeat = Math.max(totalBeats, Math.ceil(canvasW / pixelsPerBeat) + 4);
-    for (let beat = 0; beat <= gridEndBeat; beat += snapBeats) {
+    for (let beat = 0; beat <= totalBeats; beat += snapBeats) {
       const x = beat * pixelsPerBeat;
       if (x > drawWidth) break;
       const isBar = beat % timeSigNum === 0;
@@ -4697,7 +4680,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     const ctx = canvas.getContext('2d');
     const dpr = window.devicePixelRatio || 1;
     const h = 80;
-    canvas.width = Math.max(drawWidth, gridViewWidth) * dpr;
+    canvas.width = drawWidth * dpr;
     canvas.height = h * dpr;
     ctx.scale(dpr, dpr);
 
@@ -5348,8 +5331,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
 
   const renderBarLabels = () => {
     const labels = [];
-    const extraBars = Math.max(0, Math.ceil((gridViewWidth - drawWidth) / (4 * pixelsPerBeat)) + 2);
-    const barsCount = Math.ceil(totalBeats / 4) + extraBars;
+    const barsCount = Math.ceil(totalBeats / 4);
     for (let bar = 0; bar < barsCount; bar++) {
       const x = bar * 4 * pixelsPerBeat;
       labels.push(
@@ -5454,7 +5436,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     }
   }, /*#__PURE__*/React.createElement("div", {
     style: {
-      width: `${cssWidth}px`,
+      width: `${drawWidth}px`,
       height: '100%'
     },
     className: "relative h-full font-mono text-[9px] text-zinc-500 font-bold"
@@ -5474,7 +5456,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     className: "flex-1 overflow-auto bg-[#141414] min-w-0"
   }, /*#__PURE__*/React.createElement("div", {
       style: {
-        width: `${cssWidth}px`,
+        width: `${drawWidth}px`,
         height: `${(128 - PITCH_START) * NoteHeight}px`
     },
     className: "relative"
@@ -5494,7 +5476,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     className: "flex-1 overflow-x-hidden min-w-0"
   }, /*#__PURE__*/React.createElement("div", {
     style: {
-      width: `${cssWidth}px`,
+      width: `${drawWidth}px`,
       height: '100%'
     },
     className: "relative"