feat(canvas): 优化模型选择器和画布助手设置面板

- 模型选择器添加模糊匹配和图标显示支持OpenAI、Claude、Gemini
- 模型选择器下拉滚动条改为更窄的轻量样式
- 画布助手生图设置弹层调整为紧凑图像设置面板避免裁切问题
- 画布节点设置面板打开时隐藏悬浮工具条避免遮挡

web/src/app/(user)/canvas/components/canvas-assistant-panel.tsx

@@ -404,7 +404,7 @@ function AssistantComposer({
             {mode === "image" ? (
               <>
                 <ModelPicker config={config} value={config.imageModel || config.model} onChange={(model) => onConfigChange("imageModel", model)} onMissingConfig={onMissingConfig} />
-                <CanvasImageSettingsPopover config={config} onConfigChange={onConfigChange} onMissingConfig={onMissingConfig} />
+                <CanvasImageSettingsPopover config={config} placement="topRight" getPopupContainer={() => document.body} onConfigChange={onConfigChange} onMissingConfig={onMissingConfig} />
               </>
             ) : (
               <ModelPicker config={config} value={config.textModel || config.model} onChange={(model) => onConfigChange("textModel", model)} onMissingConfig={onMissingConfig} />

web/src/app/(user)/canvas/components/canvas-image-settings-popover.tsx

@@ -152,7 +152,7 @@ function AspectIcon({ type, width, height, color }: { type: string; width: numbe
   const boxHeight = ratio >= 1 ? Math.max(12, 28 / ratio) : 28;
   return (
     <span className="grid h-8 w-10 place-items-center">
-      <span className="rounded-md border-2" style={{ width: boxWidth, height: boxHeight, borderColor: color }} />
+      <span className="border-2" style={{ width: boxWidth, height: boxHeight, borderColor: color }} />
     </span>
   );
 }