Fix: cancel native dragstart on touch devices to enforce hold delay

The sections have draggable="true" which triggers native HTML5 drag
on touch with zero delay, bypassing our 1000ms hold-to-drag logic
entirely. This was most noticeable with collapsed sections where a
brief touch-and-drag instantly reordered them. Now native dragstart
is cancelled on touch devices, forcing all touch reordering through
the hold delay path.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/javascript/controllers/dashboard_sortable_controller.js

@@ -22,12 +22,22 @@ export default class extends Controller {
 
   // ===== Mouse Drag Events =====
   dragStart(event) {
+    // On touch devices, cancel native drag — use touch events with hold delay instead
+    if (this.isTouchDevice()) {
+      event.preventDefault();
+      return;
+    }
+
     this.draggedElement = event.currentTarget;
     this.draggedElement.classList.add("opacity-50");
     this.draggedElement.setAttribute("aria-grabbed", "true");
     event.dataTransfer.effectAllowed = "move";
   }
 
+  isTouchDevice() {
+    return "ontouchstart" in window || navigator.maxTouchPoints > 0;
+  }
+
   dragEnd(event) {
     event.currentTarget.classList.remove("opacity-50");
     event.currentTarget.setAttribute("aria-grabbed", "false");