feat(canvas-node): enhance input area styling and improve cursor visibility in prompt panel

web/src/components/canvas/canvas-config-composer.tsx

@@ -120,7 +120,7 @@ export function CanvasConfigComposer({ value, inputs, onChange, onClose }: Canva
                 </div>
                 <Button size="small" type="text" className="!h-7 !w-7 !min-w-7 !p-0" icon={<X className="size-3.5" />} onClick={onClose} />
             </div>
-            <div className="relative rounded-xl border" style={{ background: theme.node.fill, borderColor: theme.node.stroke }}>
+            <div className="relative rounded-xl">
                 {!value.trim() ? <div className="pointer-events-none absolute left-3 top-2 text-sm leading-7" style={{ color: theme.node.placeholder }}>输入提示词，按 @ 引用连接的图片或文本</div> : null}
                 <div
                     ref={editorRef}