fix(ctxmenu): Esc with the context menu open closes only the menu

Same Esc fall-through class: the menu's Esc handler was bubble-phase and
didn't stop the keystroke, so the slideover capture handler fired first and
popped the discard prompt while the menu also hid. Capture + stopPropagation,
gated on the menu being visible; registered before the slideover handler
(installCustomContextMenu runs at the top of init) so ordering is guaranteed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

js/app.js

@@ -6979,9 +6979,15 @@ function installCustomContextMenu() {
     document.addEventListener('mousedown', ev => {
         if (!ev.target.closest('.custom-ctxmenu')) hide();
     });
+    // Capture + stopPropagation: Esc with the menu open must close ONLY the
+    // menu — otherwise the same keystroke reaches the slideover/fallback
+    // handlers and also closes (or discard-prompts) whatever is behind.
     document.addEventListener('keydown', ev => {
-        if (ev.key === 'Escape') hide();
-    });
+        if (ev.key !== 'Escape') return;
+        if (menu.classList.contains('is-hidden')) return;
+        ev.stopPropagation();
+        hide();
+    }, true);
     window.addEventListener('blur', hide);
 }