Fix tutorial tooltip flash at 0,0 and slow step transitions

- Hide tooltip/ring with visibility:hidden until first step is positioned
- Hide tooltip between steps when scrolling to prevent stale position flash
- Replace scrollend event (poor browser support, 500ms fallback) with
  requestAnimationFrame polling that resolves in ~50ms when scroll settles

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

server/src/wled_controller/static/js/features/tutorials.js

@@ -104,6 +104,14 @@ export function startTutorial(config) {
         onClose: config.onClose || null
     });
 
+    // Hide tooltip and ring until first step positions them (prevents flash at 0,0)
+    const tooltip = overlay.querySelector('.tutorial-tooltip');
+    const ring = overlay.querySelector('.tutorial-ring');
+    const backdrop = overlay.querySelector('.tutorial-backdrop');
+    if (tooltip) tooltip.style.visibility = 'hidden';
+    if (ring) ring.style.visibility = 'hidden';
+    if (backdrop) backdrop.style.clipPath = 'none';
+
     overlay.classList.add('active');
     document.addEventListener('keydown', handleTutorialKey);
     showTutorialStep(0);
@@ -276,19 +284,25 @@ function _positionSpotlight(target, overlay, step, index, isFixed) {
 
     if (tooltip) {
         positionTutorialTooltip(tooltip, x, y, w, h, step.position, isFixed);
+        tooltip.style.visibility = '';
     }
+    if (ring) ring.style.visibility = '';
 }
 
-/** Wait for smooth scroll to finish, then resolve. */
-function _waitForScrollEnd(scrollTarget) {
+/** Wait for scroll to settle (position stops changing). */
+function _waitForScrollEnd() {
     return new Promise(resolve => {
-        let timer = setTimeout(resolve, 500); // fallback
-        const onEnd = () => {
-            clearTimeout(timer);
-            scrollTarget.removeEventListener('scrollend', onEnd);
-            resolve();
-        };
-        scrollTarget.addEventListener('scrollend', onEnd, { once: true });
+        let lastY = window.scrollY;
+        let stableFrames = 0;
+        const fallback = setTimeout(resolve, 300);
+        function check() {
+            const y = window.scrollY;
+            if (y === lastY) stableFrames++;
+            else { stableFrames = 0; lastY = y; }
+            if (stableFrames >= 3) { clearTimeout(fallback); resolve(); }
+            else requestAnimationFrame(check);
+        }
+        requestAnimationFrame(check);
     });
 }
 
@@ -321,8 +335,11 @@ function showTutorialStep(index, direction = 1) {
     const needsScroll = preRect.bottom > window.innerHeight || preRect.top < headerH;
 
     if (needsScroll) {
+        // Hide tooltip while scrolling to prevent stale position flash
+        const tt = overlay.querySelector('.tutorial-tooltip');
+        if (tt) tt.style.visibility = 'hidden';
         target.scrollIntoView({ behavior: 'smooth', block: 'center' });
-        _waitForScrollEnd(isFixed ? document.scrollingElement || document.documentElement : activeTutorial.container).then(() => {
+        _waitForScrollEnd().then(() => {
             if (activeTutorial && activeTutorial.step === index) {
                 _positionSpotlight(target, overlay, step, index, isFixed);
             }