cleanup: merge-tab empty state — DOM-built instead of innerHTML template

When mergeFiles is empty, the renderer dropped an inline-styled
innerHTML template into #mergeFileList:

  <div class="empty-state" style="padding: 40px 20px;">
    <svg style="opacity:0.3" ...><path ...></svg>
    <p style="margin-top:10px">${UI_TEXT.merge.empty}</p>
  </div>

Three issues:
- innerHTML interpolating a locale string (lint hook flags pattern
  even though locale strings are app-controlled)
- Inline styles for padding / opacity / margin
- The same SVG icon as the static HTML, duplicated

Built via createElement + createElementNS for the SVG namespace, so
the renderer never touches innerHTML for this branch. Styling moved
to a .merge-empty-state class that scopes the padding override
(needed because the merge file-list sits in a settings-card with
its own padding) without leaking into the global .empty-state used
by the VOD grid.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/renderer.ts

@@ -1561,12 +1561,23 @@ function renderMergeFiles(): void {
     byId('btnMerge').disabled = mergeFiles.length < 2;
 
     if (mergeFiles.length === 0) {
-        list.innerHTML = `
+        // Build via DOM API to keep the renderer clean of inline-styled
-            <div class="empty-state" style="padding: 40px 20px;">
+        // HTML strings. The empty-state SVG is the same plus-icon the
-                <svg width="48" height="48" viewBox="0 0 24 24" fill="currentColor" style="opacity:0.3"><path d="M19 13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z"/></svg>
+        // static HTML uses, just built programmatically.
-                <p style="margin-top:10px">${UI_TEXT.merge.empty}</p>
+        list.replaceChildren();
-            </div>
+        const wrap = document.createElement('div');
-        `;
+        wrap.className = 'empty-state merge-empty-state';
+        const svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
+        svg.setAttribute('viewBox', '0 0 24 24');
+        svg.setAttribute('fill', 'currentColor');
+        const path = document.createElementNS('http://www.w3.org/2000/svg', 'path');
+        path.setAttribute('d', 'M19 13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z');
+        svg.appendChild(path);
+        wrap.appendChild(svg);
+        const p = document.createElement('p');
+        p.textContent = UI_TEXT.merge.empty;
+        wrap.appendChild(p);
+        list.appendChild(wrap);
         return;
     }
 

src/styles.css

@@ -2086,6 +2086,23 @@ select option {
     line-height: 1.4;
 }
 
+/* Merge-tab empty state — uses the global .empty-state base and adds
+   its own padding override since the merge file-list container sits
+   inside a settings-card with its own padding. */
+.merge-empty-state {
+    padding: 40px 20px;
+}
+
+.merge-empty-state svg {
+    opacity: 0.3;
+    width: 48px;
+    height: 48px;
+}
+
+.merge-empty-state p {
+    margin-top: 10px;
+}
+
 /* Old generic scrollbar rules were dead — superseded by the
    purple-themed *::-webkit-scrollbar block further down the file.
    Removed to avoid confusion when someone greps for scrollbar styles. */