PageScene: route PoseModeSelector through getActiveEditor()

The Enter Pose Mode button reached through a window.__mouseControls
global handle that MouseControls' constructor set up. With
getActiveEditor() already exposing the live editor instance for
non-React callers (used in the camera-view toggle, the keymap),
the global is unnecessary.

Drop the (window as any).__mouseControls = this assignment in
MouseControls and the matching Window augmentation in
PoseModeSelector. Replace the click handler's reach with
getActiveEditor()?.mouse_controls?.toggleFKMode() — same shape
the keymap entry already uses.

frontend/apps/artcraft/app/src/pages/PageScene/comps/PoseModeSelector.tsx

@@ -4,14 +4,7 @@ import { Tooltip } from "@storyteller/ui-tooltip";
 import { Button } from "@storyteller/ui-button";
 import { faCheck, faPersonRunning } from "@fortawesome/pro-solid-svg-icons";
 import { usePageSceneStore } from "../PageSceneStore";
-
-declare global {
-  interface Window {
-    __mouseControls?: {
-      toggleFKMode: () => void;
-    };
-  }
-}
+import { getActiveEditor } from "../contexts/EngineContext/EngineContext";
 
 interface PoseModeSelectorProps {}
 
@@ -26,7 +19,7 @@ export const PoseModeSelector: React.FC<PoseModeSelectorProps> = () => {
 
   const handleModeChange = () => {
     setPoseMode(poseMode === "select" ? "pose" : "select");
-    window.__mouseControls?.toggleFKMode();
+    getActiveEditor()?.mouse_controls?.toggleFKMode();
   };
 
   if (!showPoseControls) {

frontend/apps/artcraft/app/src/pages/PageScene/engine/keybinds_controls.ts

@@ -152,10 +152,6 @@ export class MouseControls {
       scene: this.scene,
       onDragChange: this.onFKControlsDragging.bind(this),
     });
-
-    // Expose handlePoseModeChange to window
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    (window as any).__mouseControls = this;
   }
 
   onFKControlsDragging(dragging: boolean) {