fix: TOC scroll navigation in published articles

- Add scroll-behavior: smooth and scroll-padding-top: 80px to html
- Add click handlers on TOC links with smooth scroll and proper offset
- Guard lightbox JS against missing elements to prevent script crash
that could block TOC initialization

Made-with: Cursor

backend/src/publisher/html-renderer.ts

@@ -111,7 +111,7 @@ ${css.reset}
 
 /* Published page global reset (not needed in editor where MUI handles body) */
 body { font-family: var(--default-font-family); color: var(--text-color); }
-html { font-size: 16px; line-height: 1.6; background-color: var(--page-bg); overflow-x: hidden; }
+html { font-size: 16px; line-height: 1.6; background-color: var(--page-bg); overflow-x: hidden; scroll-behavior: smooth; scroll-padding-top: 80px; }
 
 ${css.editorTokens}
 ${css.base}
@@ -618,11 +618,14 @@ dialog.lightbox img { max-width: 95vw; max-height: 90vh; object-fit: contain; bo
     document.querySelectorAll('.tiptap img').forEach(function(img) {
       img.style.cursor = 'zoom-in';
       img.addEventListener('click', function() {
-        document.getElementById('lightbox-img').src = img.src;
-        document.getElementById('lightbox').showModal();
+        var lbImg = document.getElementById('lightbox-img');
+        var lbDlg = document.getElementById('lightbox');
+        if (lbImg) lbImg.src = img.src;
+        if (lbDlg && lbDlg.showModal) lbDlg.showModal();
       });
     });
-    document.getElementById('lightbox').addEventListener('click', function(e) { if (e.target === this) this.close(); });
+    var lb = document.getElementById('lightbox');
+    if (lb) lb.addEventListener('click', function(e) { if (e.target === this) this.close(); });
 
     // Glossary
     document.querySelectorAll('[data-type="glossary"]').forEach(function(el) { el.setAttribute('tabindex', '0'); });
@@ -678,6 +681,21 @@ dialog.lightbox img { max-width: 95vw; max-height: 90vh; object-fit: contain; bo
       holderMobile ? Array.from(holderMobile.querySelectorAll('a')) : []
     );
 
+    // Click handler for smooth scroll with offset
+    var SCROLL_OFFSET = 80;
+    allLinks.forEach(function(link) {
+      link.addEventListener('click', function(e) {
+        var href = link.getAttribute('href');
+        if (!href || href.charAt(0) !== '#') return;
+        var el = document.getElementById(href.slice(1));
+        if (!el) return;
+        e.preventDefault();
+        var top = el.getBoundingClientRect().top + window.scrollY - SCROLL_OFFSET;
+        window.scrollTo({ top: top, behavior: 'smooth' });
+        history.pushState(null, '', href);
+      });
+    });
+
     // ---- Auto-collapse logic ----
     var isMobile = window.matchMedia('(max-width: 1100px)');