XL landscape breakpoint (≥1800px): double sidebar widths + scale content

- _base.scss: new @media (orientation:landscape) and (min-width:1800px) block —
  sidebars 4rem→8rem; navbar btn 3rem→5rem; brand h1 1.2rem→2.4rem; navbar-text
  0.65rem→1.3rem; footer icons 1.75rem→3rem; nav gap 3rem→4rem; footer-container
  0.55rem→0.85rem; container margins 4rem→8rem; h2 portrait-style (2rem, centred)
- _applets.scss: gear btn right 0.5rem→2.5rem; menus right 0.5rem→2rem at ≥1800px
- _game-kit.scss: kit btn right 0.5rem→2.5rem at ≥1800px
- _room.scss: sig-overlay padding-left 4rem→8rem at ≥1800px
- _tray.scss: tray wrap left/right 4rem→8rem at ≥1800px
- room.js: sizeSigModal right inset 64px→128px at ≥1800px viewport width

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

src/apps/epic/static/apps/epic/room.js

@@ -61,11 +61,13 @@
             }
         });
 
-        // Landscape: right clears gear/kit buttons (~4rem); bottom is fixed 60px for
-        // the kit-bag handle strip — tray is ignored so the stage has room to breathe.
+        // Landscape: right clears gear/kit buttons; bottom is fixed 60px for the
+        // kit-bag handle strip — tray is ignored so the stage has room to breathe.
+        // At ≥1800px the right sidebar doubles to 8rem so clear 128px.
         if (isLandscape) {
-            rightInset  = Math.max(rightInset, 64);  // 4rem
-            bottomInset = 60;                         // kit-bag handle
+            var xlBreak = vw >= 1800;
+            rightInset  = Math.max(rightInset, xlBreak ? 128 : 64);
+            bottomInset = 60;
         }
 
         overlay.style.paddingRight  = rightInset  + 'px';