Add MCP combo button to the level editor toolbar

A "MCP" combo button in the top toolbar (LevelEditor.LevelEditorToolBar.User)
opens a dropdown with:
- Status: live Remote Control reachability (:30010, green/red) + re-check, and a
  "Start Remote Control server" action.
- Active tools (N): submenu listing the catalogue from tools.json (name + desc).
- Settings: opens the Setup Wizard tab.

The bridge ping is refactored into PingRc(bool) so it can update a cached status
silently (menu open) or with the startup notification.

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

Source/UEBlueprintMCPEditor/Public/UEBlueprintMCPEditor.h

@@ -17,8 +17,14 @@ public:
 private:
     friend class FMCPZoneInputProcessor;
 
+    enum class EMcpRcStatus : uint8 { Unknown, Up, Down };
+
     void RegisterMenus();
     void RegisterWizardTabAndMenu();
+    void RegisterMCPToolbarButton();
+    void BuildMCPStatusMenu(class UToolMenu* Menu);
+    void BuildToolsSubMenu(class UToolMenu* Menu);
+    void PingRc(bool bNotify);
     TSharedRef<class SDockTab> SpawnWizardTab(const class FSpawnTabArgs& Args);
     void NotifyBridgeStatus();
     void ToggleMCPZoneMode(TWeakPtr<FBlueprintEditor> BlueprintEditor);
@@ -29,6 +35,7 @@ private:
 
     bool bMCPZoneModeActive = false;
     bool bWizardTabRegistered = false;
+    EMcpRcStatus CachedRcStatus = EMcpRcStatus::Unknown;
     TWeakPtr<FBlueprintEditor> ActiveMCPZoneEditor;
     TSharedPtr<IInputProcessor> MCPZoneInputProcessor;
 };