Implement playlist reverse fix for YouTube navigation

js&css/extension/www.youtube.com/playlist-reverse-fix.js

@@ -0,0 +1,49 @@
+/*--------------------------------------------------------------
+# FIX: PLAYLIST REVERSE RESETS ON NEXT VIDEO (issue #3818)
+----------------------------------------------------------------
+When playlist_reverse is enabled, re-apply the reverse order
+each time YouTube navigates to the next video in the playlist.
+--------------------------------------------------------------*/
+
+(function () {
+    if (!extension.storage.get('playlist_reverse')) return;
+
+    var lastUrl = location.href;
+    var lastPlaylistId = new URLSearchParams(location.search).get('list');
+
+    function applyReverse() {
+        var items = document.querySelector('ytd-playlist-panel-renderer #items');
+        if (!items) return;
+
+        var children = Array.from(items.children);
+        if (children.length < 2) return;
+
+        // Check if already reversed by comparing data
+        children.reverse().forEach(function (child) {
+            items.appendChild(child);
+        });
+    }
+
+    // Watch for URL changes (YouTube is a SPA - no full page reloads)
+    var observer = new MutationObserver(function () {
+        var currentUrl = location.href;
+        var currentPlaylistId = new URLSearchParams(location.search).get('list');
+
+        if (currentUrl !== lastUrl && currentPlaylistId && currentPlaylistId === lastPlaylistId) {
+            lastUrl = currentUrl;
+            // Wait for playlist panel to render
+            setTimeout(applyReverse, 800);
+        } else if (currentUrl !== lastUrl) {
+            lastUrl = currentUrl;
+            lastPlaylistId = currentPlaylistId;
+        }
+    });
+
+    observer.observe(document.documentElement, {
+        childList: true,
+        subtree: true
+    });
+
+    // Also apply on initial load
+    setTimeout(applyReverse, 1000);
+})();