Keep the watch party panel above the bottom bars so its leave button is reachable

frontend/app.js

@@ -5584,7 +5584,6 @@ const SectionRail = (() => {
   // guessing an offset that is wrong on the next phone.
   function placeRail() {
     const r = rail();
-    if (!r || r.classList.contains('hidden')) return;
     let occupied = 0;
     for (const id of ['bottomNav', 'miniBar']) {
       const el = document.getElementById(id);
@@ -5597,7 +5596,10 @@ const SectionRail = (() => {
     const want = Math.round(occupied + 14);
     if (st.bottom !== want) {
       st.bottom = want;
-      r.style.setProperty('--rail-bottom', want + 'px');
+      if (r) r.style.setProperty('--rail-bottom', want + 'px');
+      // Published for anything else that must sit above the bottom bars —
+      // the watch-party panel's leave button was hidden behind them.
+      document.documentElement.style.setProperty('--bottom-chrome', Math.round(occupied) + 'px');
     }
   }