fix(gallery): open lightbox on click and keep mouse drag alive

Pointer capture on pointerdown redirected the click to the strip, so photos
never opened; capture now starts only after a 5px drag. Native link drag is
blocked so it no longer cancels the mouse drag.

site/assets/js/main.js

@@ -829,15 +829,22 @@ document.addEventListener('DOMContentLoaded', function () {
             if (e.pointerType === 'touch' || e.button !== 0) return;
             dragging = true; moved = 0;
             startX = e.clientX; startLeft = wrap.scrollLeft;
-            wrap.classList.add('is-dragging');
-            wrap.setPointerCapture(e.pointerId);
         });
         wrap.addEventListener('pointermove', function (e) {
             if (!dragging) return;
             var dx = e.clientX - startX;
             moved = Math.max(moved, Math.abs(dx));
+            if (moved <= 5) return;
+            // Capture only once it is a real drag: capturing on pointerdown sends the
+            // click to .gal-wrap instead of the photo, so the lightbox never opened.
+            if (!wrap.classList.contains('is-dragging')) {
+                wrap.classList.add('is-dragging');
+                try { wrap.setPointerCapture(e.pointerId); } catch (err) {}
+            }
             wrap.scrollLeft = startLeft - dx;
         });
+        // The tiles are links, which the browser drags natively (cancelling our drag).
+        wrap.addEventListener('dragstart', function (e) { e.preventDefault(); });
         function endDrag(e) {
             if (!dragging) return;
             dragging = false;