리펙토링: 전체 구조 검토, 개선

src/renderer/handlers/file-explorer.js

@@ -125,7 +125,14 @@ async function expandNode(nodeEl, autoExpandPath) {
   if (!childrenEl.dataset.loaded) {
     childrenEl.dataset.loaded = 'true';
     const dirs = await window.api.listDirectories(nodeEl.dataset.path);
-    dirs.forEach(dir => childrenEl.appendChild(createNode(dir)));
+    if (dirs === null) {
+      const err = document.createElement('div');
+      err.className = 'tree-access-error';
+      err.textContent = '접근 불가';
+      childrenEl.appendChild(err);
+    } else {
+      dirs.forEach(dir => childrenEl.appendChild(createNode(dir)));
+    }
   }
 
   // Auto-expand toward the target path

src/renderer/handlers/selection.js

@@ -4,9 +4,15 @@ let _state, _cb;
 let rbActive = false;
 let rbStartX = 0;
 let rbStartY = 0;
+let _rafPending   = false;
+let _lastMoveEvent = null;
 
 let lastSelectedIdx = null;
 
+export function resetAnchor() {
+  lastSelectedIdx = null;
+}
+
 export function init({ gridContainer, rubberBand, grid, state, callbacks }) {
   _rubberBand = rubberBand;
   _grid       = grid;
@@ -98,6 +104,17 @@ function _onStart(e) {
 
 function _onMove(e) {
   if (!rbActive) return;
+  _lastMoveEvent = e;
+  if (!_rafPending) {
+    _rafPending = true;
+    requestAnimationFrame(_processMove);
+  }
+}
+
+function _processMove() {
+  _rafPending = false;
+  const e = _lastMoveEvent;
+  if (!rbActive || !e) return;
 
   const left   = Math.min(rbStartX, e.clientX);
   const top    = Math.min(rbStartY, e.clientY);
@@ -110,11 +127,11 @@ function _onMove(e) {
   });
 
   const sel = { left, top, right: left + width, bottom: top + height };
+  const preserve = e.shiftKey || e.ctrlKey || e.metaKey;
   Array.from(_grid.children).forEach((card, i) => {
     const r = card.getBoundingClientRect();
     const overlaps = !(r.right < sel.left || r.left > sel.right ||
                        r.bottom < sel.top  || r.top  > sel.bottom);
-    const preserve = e.shiftKey || e.ctrlKey || e.metaKey;
     if (overlaps) {
       _state.selectedIdxs.add(i);
     } else if (!preserve) {