refactor(canvas): derive toolbar offsets from panel geometry

app/canvas/[id]/page.tsx

@@ -79,6 +79,10 @@ const SIZE_PRESETS = [
   { label: "9:16", value: "9:16", width: 1024, height: 1820 },
 ];
 
+const FLOATING_PANEL_WIDTH = 460;
+const FLOATING_PANEL_INSET = 16;
+const FLOATING_UI_GAP = 16;
+
 export default function CanvasEditorPage({ params }: PageProps) {
   // 使用 useParams 确保客户端导航时能正确获取更新的 id
   const routeParams = useParams();
@@ -124,6 +128,7 @@ export default function CanvasEditorPage({ params }: PageProps) {
   const [isPanelOpen, setIsPanelOpen] = useState(true);
   // 面板模式: 'chat' 聊天面板, 'fileList' 文件列表
   const [panelMode, setPanelMode] = useState<'chat' | 'fileList'>('chat');
+  const [viewportWidth, setViewportWidth] = useState(0);
 
   const { data: siteSettingsData } = useSWR<{
     siteName?: string;
@@ -145,6 +150,13 @@ export default function CanvasEditorPage({ params }: PageProps) {
     ? nodes.find(n => n.id === selectedNodeIds[0] && n.type === 'image')
     : null;
 
+  const resolvedPanelWidth = viewportWidth > 0
+    ? Math.min(FLOATING_PANEL_WIDTH, Math.max(viewportWidth - FLOATING_PANEL_INSET, 0))
+    : FLOATING_PANEL_WIDTH;
+  const panelOcclusionRight = isPanelOpen ? resolvedPanelWidth + FLOATING_PANEL_INSET : 0;
+  const floatingToolbarOffset = isPanelOpen ? -(panelOcclusionRight / 2) : 0;
+  const compactControlsRight = isPanelOpen ? panelOcclusionRight + FLOATING_UI_GAP : FLOATING_UI_GAP;
+
   // 加载画布数据
   useEffect(() => {
     console.log('[Canvas] Loading project:', id);
@@ -179,6 +191,13 @@ export default function CanvasEditorPage({ params }: PageProps) {
     loadProject();
   }, [id]); // 只依赖 id，使用 getState() 直接调用 store actions
 
+  useEffect(() => {
+    const updateViewportWidth = () => setViewportWidth(window.innerWidth);
+    updateViewportWidth();
+    window.addEventListener("resize", updateViewportWidth);
+    return () => window.removeEventListener("resize", updateViewportWidth);
+  }, []);
+
   const persistCanvasState = useCallback(
     async (reason: "autosave" | "delete" | "beforeunload") => {
       const canvasData = getCanvasState();
@@ -561,7 +580,7 @@ export default function CanvasEditorPage({ params }: PageProps) {
         
         {/* 1. Canvas Layer (Full Screen) - 使用 key 强制在 id 变化时重新挂载 */}
         <div className="absolute inset-0 z-0" key={`workspace-${id}`}>
-           <CanvasWorkspace occlusionRight={isPanelOpen ? 476 : 0} />
+           <CanvasWorkspace occlusionRight={panelOcclusionRight} />
         </div>
 
         {/* Brand Entry (Top Left) */}
@@ -641,7 +660,7 @@ export default function CanvasEditorPage({ params }: PageProps) {
 
         {/* 3. Floating Actions (Top Right) */}
         {!isPanelOpen && (
-          <div className="absolute top-4 right-4 z-20">
+          <div className="absolute z-20" style={{ top: FLOATING_PANEL_INSET, right: FLOATING_PANEL_INSET }}>
             <Tooltip>
               <TooltipTrigger asChild>
                 <Button
@@ -660,9 +679,16 @@ export default function CanvasEditorPage({ params }: PageProps) {
 
         {/* 4. Floating Sidebar (Right) */}
         <div className={cn(
-            "absolute top-4 right-4 bottom-4 z-10 w-[460px] max-w-[calc(100vw-1rem)] transition-all duration-300 ease-in-out",
+            "absolute z-10 transition-all duration-300 ease-in-out",
             isPanelOpen ? "translate-x-0 opacity-100" : "translate-x-[120%] opacity-0 pointer-events-none"
-        )}>
+        )}
+        style={{
+          top: FLOATING_PANEL_INSET,
+          right: FLOATING_PANEL_INSET,
+          bottom: FLOATING_PANEL_INSET,
+          width: FLOATING_PANEL_WIDTH,
+          maxWidth: `calc(100vw - ${FLOATING_PANEL_INSET}px)`,
+        }}>
             <div className="h-full w-full rounded-2xl border bg-white dark:bg-zinc-950 shadow-2xl overflow-hidden flex flex-col">
               {panelMode === 'chat' ? (
                 // AI 对话内容 - 使用 key 强制在 id 变化时重新挂载
@@ -687,9 +713,7 @@ export default function CanvasEditorPage({ params }: PageProps) {
         <div className="absolute bottom-5 left-1/2 z-20 -translate-x-1/2">
           <div
             className="flex items-center gap-1 rounded-[24px] border bg-background/88 px-2.5 py-1.5 shadow-2xl backdrop-blur-md"
-            style={{
+            style={{ marginLeft: `${floatingToolbarOffset}px` }}
-              marginLeft: isPanelOpen ? "-238px" : "0px",
-            }}
           >
             <Tooltip>
               <TooltipTrigger asChild>
@@ -797,7 +821,7 @@ export default function CanvasEditorPage({ params }: PageProps) {
         {/* 6. Bottom Right Compact Controls */}
         <div
           className="absolute bottom-5 z-20"
-          style={{ right: isPanelOpen ? "492px" : "16px" }}
+          style={{ right: `${compactControlsRight}px` }}
         >
           <div className="flex items-center gap-1 rounded-2xl border bg-background/88 px-2 py-1.5 shadow-xl backdrop-blur-md">
             <Tooltip>