fix: disabled-state UI, settings shallow-merge, and popup save reliability

Co-authored-by: Cursor <cursoragent@cursor.com>

content/main.js

@@ -5,6 +5,7 @@
     const settings = await window.RedditTweaks.loadSettings();
     if (!settings.enabled) return;
 
+    document.documentElement.classList.add("rt-enabled");
     window.RedditTweaks.badgeTweak.apply(settings);
 
     browser.storage.onChanged.addListener(function (changes) {

content/styles/badges.css

@@ -1,6 +1,6 @@
 /* --- FOUC prevention: hide original elements immediately --- */
-.thing.link .tagline .subreddit,
-.thing.link .flat-list .comments {
+html.rt-enabled .thing.link .tagline .subreddit,
+html.rt-enabled .thing.link .flat-list .comments {
   display: none !important;
 }