Fix Firefox layout bug with compact mark-watched button (#244)

Firefox handles position:relative on flex items differently from Chrome,
causing metadata to shrink on short titles and the button to float away.
Wrap the menu button contents in an inner div that holds position:relative
instead of applying it directly to the flex item.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: OsaSoft

subs.css

@@ -98,7 +98,7 @@ ytd-grid-video-renderer.style-scope.ytd-grid-renderer:hover .subs-btn-mark-watch
 }
 
 /* Compact layout: positioned below the triple dots menu */
-.yt-lockup-metadata-view-model__menu-button {
+.subs-btn-compact-wrapper {
   position: relative;
 }
 

videos/SubscriptionsVideo.js

@@ -56,9 +56,18 @@ class SubscriptionVideo extends Video {
                 ? verticalDiv.querySelector(".yt-lockup-metadata-view-model__menu-button")
                 : null;
             if (menuButtonDiv) {
-                // Compact layout: place inside the menu button area (next to triple dots)
+                // Compact layout: place inside a wrapper to avoid position:relative on flex item (Firefox bug)
                 container.classList.add("subs-btn-container--compact");
-                menuButtonDiv.appendChild(container);
+                let wrapper = menuButtonDiv.querySelector(".subs-btn-compact-wrapper");
+                if (!wrapper) {
+                    wrapper = document.createElement("div");
+                    wrapper.classList.add("subs-btn-compact-wrapper");
+                    while (menuButtonDiv.firstChild) {
+                        wrapper.appendChild(menuButtonDiv.firstChild);
+                    }
+                    menuButtonDiv.appendChild(wrapper);
+                }
+                wrapper.appendChild(container);
             } else {
                 // Default layout: insert after metadata div
                 let metadataDiv = verticalDiv.querySelector(":scope > .yt-lockup-view-model__metadata");