XL landscape: revert tray to landscape style; fix sig-stage stretch

- Remove _tray.scss XL (≥1800px) portrait override block entirely
- _isLandscape() no longer returns false at ≥1800px — tray uses
  landscape slide-from-top at all wide landscape widths
- sig-stage: align-self: stretch (was center) so JS sizeSigCard()
  measures correct stage width; card size no longer collapses
- Position strip: horizontal row at top (was vertical column-reverse)
- sig-overlay/sig-stage/sig-deck-grid layout polish at 1100px/1800px

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

src/apps/epic/static/apps/epic/tray.js

@@ -40,9 +40,6 @@ var Tray = (function () {
 
     function _isLandscape() {
         if (_landscapeOverride !== null) return _landscapeOverride;
-        // ≥1800px uses portrait-style tray (slides from right) to match the
-        // doubled sidebar widths and XL tray CSS reset.
-        if (window.innerWidth >= 1800) return false;
         return window.innerWidth > window.innerHeight;
     }
 
@@ -97,10 +94,7 @@ var Tray = (function () {
             // Closed: tray hidden above viewport, handle visible at y=0.
             _maxTop = -(gearBtnTop - handleH);
         } else {
-            // Portrait (and XL landscape, which uses portrait-style tray):
-            // Wrap width = viewportW so the closed right edge reaches the viewport boundary.
-            // The footer sidebar (z-100) is above the wrap (z-95) and has a solid background,
-            // so the handle parks behind it and slides out from under it when opened.
+            // Portrait: wrap width = full viewport; handle parks at right edge.
             var handleW = _btn.offsetWidth || 48;
             if (_wrap) _wrap.style.width = window.innerWidth + 'px';
             _minLeft = 0;