fix: keep detail mode workbench anchored at composer bottom

components/canvas/CanvasChatPanel.tsx

@@ -5448,7 +5448,7 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
       
       {/* 消息列表 */}
       {isDetailEmptyState ? (
-        <div className="h-3 shrink-0" />
+        <div className="flex-1 min-h-0" />
       ) : (
       <div
         key={`${activeChatId}-${messageViewportKey}`}
@@ -5969,14 +5969,14 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
       {/* 底部输入区域 - 混合输入（图片标签+文字可自由混合） */}
       <div className="p-4 bg-background/80 backdrop-blur-md border-t">
         <div
-          className="relative bg-card rounded-3xl border transition-all duration-200 focus-within:border-primary/50 focus-within:bg-background"
+          className="relative flex flex-col bg-card rounded-3xl border transition-all duration-200 focus-within:border-primary/50 focus-within:bg-background"
           data-canvas-chat-input-anchor="true"
         >
           {isDetailGenerationMode && (
             <div
               className={cn(
-                "mx-3 overflow-y-auto rounded-2xl border border-black/10 bg-white/95 p-3 pr-2",
-                "mt-3",
+                "order-3 mx-3 mb-11 overflow-y-auto rounded-2xl border border-black/10 bg-white/95 p-3 pr-2",
+                "mt-1",
                 renderableVisibleMessages.length === 0 ? "max-h-[62vh]" : "max-h-[54vh]"
               )}
             >