PageScene: drop dead side-panel store fields

sidePanelWidth, sidePanelVisible, dndSidePanelWidth and their setters
are no longer read by any rendered component. Drop them from
PageSceneStore and the lone setSidePanelWidth(340) call in
PageEditor's mount effect. PreviewFrameImage's width calc no longer
subtracts the (always-zero) panel width.

frontend/apps/artcraft/app/src/pages/PageScene/PageEditor.tsx

@@ -112,7 +112,6 @@ export const PageEditor = () => {
   };
 
   useEffect(() => {
-    usePageSceneStore.getState().setSidePanelWidth(340);
     window.onbeforeunload = () => {
       return "You may have unsaved changes.";
     };

frontend/apps/artcraft/app/src/pages/PageScene/PageSceneStore.ts

@@ -99,9 +99,6 @@ interface PageSceneState {
   isPromptBoxFocused: boolean;
 
   // layout / panels
-  sidePanelWidth: number;
-  sidePanelVisible: boolean;
-  dndSidePanelWidth: number;
   assetModalVisible: boolean;
   assetModalVisibleDuringDrag: boolean;
   reopenAfterDrag: boolean;
@@ -168,9 +165,6 @@ interface PageSceneState {
   setIsPromptBoxFocused: (focused: boolean) => void;
 
   // layout
-  setSidePanelWidth: (px: number) => void;
-  setSidePanelVisible: (visible: boolean) => void;
-  setDndSidePanelWidth: (px: number) => void;
   setAssetModalVisible: (visible: boolean) => void;
   setAssetModalVisibleDuringDrag: (visible: boolean) => void;
   setReopenAfterDrag: (reopen: boolean) => void;
@@ -230,9 +224,6 @@ export const usePageSceneStore = create<PageSceneState>((set, get) => ({
   hotkeyStatus: { disabled: false, disabledBy: DomLevels.NONE },
   isPromptBoxFocused: false,
 
-  sidePanelWidth: 0,
-  sidePanelVisible: false,
-  dndSidePanelWidth: -1,
   assetModalVisible: false,
   assetModalVisibleDuringDrag: true,
   reopenAfterDrag: false,
@@ -328,9 +319,6 @@ export const usePageSceneStore = create<PageSceneState>((set, get) => ({
   setIsPromptBoxFocused: (focused) => set({ isPromptBoxFocused: focused }),
 
   // layout actions
-  setSidePanelWidth: (px) => set({ sidePanelWidth: px }),
-  setSidePanelVisible: (visible) => set({ sidePanelVisible: visible }),
-  setDndSidePanelWidth: (px) => set({ dndSidePanelWidth: px }),
   setAssetModalVisible: (visible) => set({ assetModalVisible: visible }),
   setAssetModalVisibleDuringDrag: (visible) =>
     set({ assetModalVisibleDuringDrag: visible }),

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

@@ -8,24 +8,18 @@ import { usePageSceneStore } from "~/pages/PageScene/PageSceneStore";
 
 export const PreviewFrameImage = () => {
   useSignals();
-  const { editorState, previewSrc, sidePanelVisible, sidePanelWidth } =
-    usePageSceneStore(
-      useShallow((s) => ({
-        editorState: s.editorState,
-        previewSrc: s.previewSrc,
-        sidePanelVisible: s.sidePanelVisible,
-        sidePanelWidth: s.sidePanelWidth,
-      })),
-    );
+  const { editorState, previewSrc } = usePageSceneStore(
+    useShallow((s) => ({
+      editorState: s.editorState,
+      previewSrc: s.previewSrc,
+    })),
+  );
 
   if (editorState !== EditorStates.PREVIEW) {
     return null;
   }
 
-  const width =
-    pageWidth.value -
-    (sidePanelVisible ? sidePanelWidth : 0) -
-    84;
+  const width = pageWidth.value - 84;
   const height = pageHeight.value - 56;
 
   if (previewSrc === "") {