perf: memoize queue sort, dedup stats scan per tick, skip no-op DOM writes

Three more wins on top of the previous pass:
  - sortQueueJobs memoizes the result for static sort keys
    (filename, host, size) — these don't change during upload, so
    every 200ms progress render now reuses the same sorted array
    instead of running an O(n log n) Collator compare.
  - _computeQueueStats caches within a single tick via queueMicrotask.
    updateStatusBar + updateStatsPanel are always called back-to-back
    and now share one queue scan instead of running two.
  - _updateRowInPlace writes DOM values only when they actually
    changed. Idle/queued/done rows (the majority) incur zero DOM
    mutations per progress tick.

eslint.config.mjs

@@ -32,6 +32,7 @@ export default [
         alert: 'readonly',
         confirm: 'readonly',
         requestAnimationFrame: 'readonly',
+        queueMicrotask: 'readonly',
         Intl: 'readonly',
         crypto: 'readonly',
         URLSearchParams: 'readonly',

renderer/app.js

@@ -874,25 +874,41 @@ function _updateRowInPlace(tr, job) {
   const pct = Math.min(100, Math.round((job.progress || 0) * 100));
   const link = job.result ? (job.result.download_url || job.result.embed_url || '') : '';
 
-  // Update row class
-  tr.className = `queue-row ${statusClass}${selectedJobIds.has(job.id) ? ' selected' : ''}`;
-  tr.dataset.link = link;
+  // Write DOM only when the target value actually changes — a no-op progress
+  // tick (same pct, same speed) then performs zero DOM work. Massive saver
+  // when most of the visible jobs are idle/queued/done and only a few are
+  // actively uploading.
+  const newClass = `queue-row ${statusClass}${selectedJobIds.has(job.id) ? ' selected' : ''}`;
+  if (tr.className !== newClass) tr.className = newClass;
+  if (tr.dataset.link !== link) tr.dataset.link = link;
 
   const cells = tr.children;
   if (cells.length < 8) return false; // structure mismatch, needs full rebuild
 
-  cells[1].textContent = uploadedSize;
+  if (cells[1].textContent !== uploadedSize) cells[1].textContent = uploadedSize;
   // cells[0] (filename) and cells[2] (hoster) don't change during upload
   const badge = cells[3].querySelector('.status-badge');
-  if (badge) { badge.className = `status-badge ${statusClass}`; badge.textContent = statusText; }
-  cells[4].textContent = elapsed;
-  cells[5].textContent = remaining;
-  cells[6].textContent = speed;
+  if (badge) {
+    const badgeClass = `status-badge ${statusClass}`;
+    if (badge.className !== badgeClass) badge.className = badgeClass;
+    if (badge.textContent !== statusText) badge.textContent = statusText;
+  }
+  if (cells[4].textContent !== elapsed) cells[4].textContent = elapsed;
+  if (cells[5].textContent !== remaining) cells[5].textContent = remaining;
+  if (cells[6].textContent !== speed) cells[6].textContent = speed;
 
   const fill = cells[7].querySelector('.progress-bar-fill');
-  if (fill) { fill.style.width = pct + '%'; fill.className = `progress-bar-fill ${statusClass}`; }
+  if (fill) {
+    const pctStr = pct + '%';
+    if (fill.style.width !== pctStr) fill.style.width = pctStr;
+    const fillClass = `progress-bar-fill ${statusClass}`;
+    if (fill.className !== fillClass) fill.className = fillClass;
+  }
   const pctSpan = cells[7].querySelector('.progress-pct');
-  if (pctSpan) pctSpan.textContent = job.status === 'preview' ? '' : pct + '%';
+  if (pctSpan) {
+    const pctText = job.status === 'preview' ? '' : pct + '%';
+    if (pctSpan.textContent !== pctText) pctSpan.textContent = pctText;
+  }
 
   return true;
 }
@@ -999,11 +1015,22 @@ function _onQueueScroll() {
 const _collatorDE = new Intl.Collator('de', { sensitivity: 'base', numeric: true });
 const _collatorSimple = new Intl.Collator('de');
 
+// Queue sort memoization. Keys that don't change during upload (filename, host,
+// size) reuse the cached result across progress-driven re-renders. Dynamic keys
+// (status/speed/progress) are recomputed each call since the sort order itself
+// moves every tick. For a queue of 1000+ jobs sorted by filename, this skips
+// the Collator-based O(n log n) sort on every 200ms progress render.
+let _queueSortCache = { sig: '', result: [] };
+const _STATIC_SORT_KEYS = new Set(['filename', 'host', 'size']);
+
 function sortQueueJobs(jobs) {
   const { key, direction } = queueSortState;
   const factor = direction === 'asc' ? 1 : -1;
+  const canCache = _STATIC_SORT_KEYS.has(key);
+  const sig = canCache ? `${key}|${direction}|${jobs.length}` : '';
+  if (sig && _queueSortCache.sig === sig) return _queueSortCache.result;
 
-  return jobs.slice().sort((a, b) => {
+  const sorted = jobs.slice().sort((a, b) => {
     let cmp = 0;
     if (key === 'filename') cmp = _collatorDE.compare(a.fileName, b.fileName);
     else if (key === 'size') cmp = (a.bytesTotal || 0) - (b.bytesTotal || 0);
@@ -1013,6 +1040,8 @@ function sortQueueJobs(jobs) {
     else if (key === 'progress') cmp = (a.progress || 0) - (b.progress || 0);
     return cmp * factor;
   });
+  if (sig) _queueSortCache = { sig, result: sorted };
+  return sorted;
 }
 
 function getStatusOrder(status) {
@@ -1968,7 +1997,14 @@ function applySummaryResults(summary) {
 
 // Single-pass queue stats computation (shared by status bar + stats panel).
 // Also tracks inProgressBytes so the status bar doesn't need a second scan.
+//
+// Memoized within a single tick: back-to-back calls (updateStatusBar +
+// updateStatsPanel fire together 4×/sec during upload) share one scan. The
+// cache is cleared on microtask so the next tick picks up fresh state.
+let _queueStatsCache = null;
 function _computeQueueStats() {
+  if (_queueStatsCache) return _queueStatsCache;
+
   let remaining = 0, inProgress = 0, done = 0, errors = 0;
   let bytesRemaining = 0, totalSize = 0, remainingSize = 0, inProgressBytes = 0;
   const total = queueJobs.length;
@@ -1999,7 +2035,9 @@ function _computeQueueStats() {
     }
   }
 
-  return { total, remaining, inProgress, done, errors, bytesRemaining, totalSize, remainingSize, inProgressBytes };
+  _queueStatsCache = { total, remaining, inProgress, done, errors, bytesRemaining, totalSize, remainingSize, inProgressBytes };
+  queueMicrotask(() => { _queueStatsCache = null; });
+  return _queueStatsCache;
 }
 
 function updateStatusBar() {