Replace mode toggle cycle with a dropdown menu

The composite mode control (#planModeBtn) now opens a dropdown menu
instead of cycling, following the emoji-picker pattern: each mode is an
entry with icon + label + description, the active one marked with a
check. Direct jumps between modes are now possible, so selecting
plan/ultracode resets the persisted panel mode to avoid running both the
panel and the CLI worker. Unified the active button states.

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

wwwroot/js/pages/chat-page.js

@@ -572,12 +572,16 @@ registerPage('chat', {
       });
     }
 
-    // Unified Modus-Toggle (Aus / Plan / Fusion / MoA) – aus der Session initialisieren
+    // Unified Modus-Menü (Aus / Plan / Ultracode / Fusion / MoA) – aus der Session initialisieren.
+    // Klick öffnet ein Dropdown (wie der Emoji-Picker), aus dem der Modus direkt gewählt wird.
     const compositeModeBtn = document.getElementById('planModeBtn');
     if (compositeModeBtn) {
       const hasPanelAgents = !!(session.panelAgentIds && String(session.panelAgentIds).trim());
       initCompositeMode(session.multiModelMode, hasPanelAgents);
-      compositeModeBtn.addEventListener('click', cycleCompositeMode);
+      compositeModeBtn.addEventListener('click', (e) => {
+        e.stopPropagation();
+        toggleCompositeMenu(compositeModeBtn);
+      });
     }
 
     // File Upload