Fix regen: capture pending slot/idx before hidePopup clears them

Root cause: document addEventListener with capture=true fired BEFORE
button onclick, so _pendingSlot was already null when fireRegen ran.

Fix: save slot/idx to locals first, use bubble phase on doc listener.

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

app.py

@@ -1705,13 +1705,15 @@ _GLOBAL_JS = """
         'border-radius:4px;padding:5px 14px;font-size:12px;cursor:pointer;width:100%;">&#10227; Regenerate</button>';
     document.body.appendChild(_popup);
     document.getElementById('_wf_popup_btn').onclick = function(e) {
-      e.stopPropagation();
-      if (_pendingSlot !== null && _pendingIdx !== null) {
-        fireRegen(_pendingSlot, _pendingIdx);
-      }
+      e.stopPropagation();  // prevents the document bubble-phase listener below from firing
+      var slot = _pendingSlot, idx = _pendingIdx;  // capture before hidePopup clears them
       hidePopup();
+      if (slot !== null && idx !== null) {
+        fireRegen(slot, idx);
+      }
     };
-    document.addEventListener('click', function() { hidePopup(); }, true);
+    // Use bubble phase (false) so stopPropagation() on the button click prevents this from firing
+    document.addEventListener('click', function() { hidePopup(); }, false);
     return _popup;
   }