feat(polaris): 完善首页背景与搜索入口视觉

使用本地背景和官方 Provider 图标，闭合状态仅展示当前图标。
调整冷蓝磨砂层次，并移除快捷卡片外部阴影以消除底部色带。
补充搜索 Provider 展示行为测试。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ts/web/nextjs/polaris/src/features/home/components/search-box.test.tsx

@@ -72,6 +72,34 @@ describe("SearchBox", () => {
     expect(input).toHaveFocus()
   })
 
+  it("闭合态只显示当前图标，展开后显示 Provider 名称", async () => {
+    const user = userEvent.setup()
+    renderSearchBox()
+    const trigger = screen.getByRole("button", {
+      name: "选择搜索方式，当前为 Google",
+    })
+
+    expect(trigger.textContent).toBe("")
+    expect(trigger.querySelector("img")).toHaveAttribute(
+      "src",
+      "/icons/google.svg",
+    )
+
+    await user.click(trigger)
+    for (const [label, icon] of [
+      ["Google", "google"],
+      ["Bing", "bing"],
+      ["GitHub", "github"],
+      ["本地", "local"],
+    ] as const) {
+      const item = screen.getByRole("menuitemradio", { name: label })
+      expect(item.querySelector("img")).toHaveAttribute(
+        "src",
+        `/icons/${icon}.svg`,
+      )
+    }
+  })
+
   it("Google 模式回车只执行当前页外部导航", async () => {
     const user = userEvent.setup()
     const { onExternalNavigate } = renderSearchBox()

ts/web/nextjs/polaris/src/features/home/components/search-provider-menu.tsx

@@ -1,12 +1,6 @@
 "use client"
 
-import {
-  Database,
-  GitFork,
-  Globe2,
-  Search,
-  type LucideIcon,
-} from "lucide-react"
+import Image from "next/image"
 
 import { Button } from "@/components/ui/button"
 import {
@@ -26,11 +20,24 @@ const PROVIDER_LABELS: Record<SearchProvider, string> = {
   local: "本地",
 }
 
-const PROVIDER_ICONS: Record<SearchProvider, LucideIcon> = {
-  google: Globe2,
-  bing: Search,
-  github: GitFork,
-  local: Database,
+const PROVIDER_ICON_PATHS: Record<SearchProvider, string> = {
+  google: "/icons/google.svg",
+  bing: "/icons/bing.svg",
+  github: "/icons/github.svg",
+  local: "/icons/local.svg",
+}
+
+function ProviderIcon({ provider }: { provider: SearchProvider }) {
+  return (
+    <Image
+      className="search-provider-menu__icon"
+      src={PROVIDER_ICON_PATHS[provider]}
+      alt=""
+      width={24}
+      height={24}
+      aria-hidden="true"
+    />
+  )
 }
 
 type SearchProviderMenuProps = {
@@ -44,8 +51,6 @@ export function SearchProviderMenu({
   enabledProviders,
   onProviderChange,
 }: SearchProviderMenuProps) {
-  const CurrentIcon = PROVIDER_ICONS[provider]
-
   return (
     <DropdownMenu>
       <DropdownMenuTrigger asChild>
@@ -55,8 +60,7 @@ export function SearchProviderMenu({
           className="search-provider-menu__trigger"
           aria-label={`选择搜索方式，当前为 ${PROVIDER_LABELS[provider]}`}
         >
-          <CurrentIcon aria-hidden="true" />
-          <span>{PROVIDER_LABELS[provider]}</span>
+          <ProviderIcon provider={provider} />
         </Button>
       </DropdownMenuTrigger>
       <DropdownMenuContent align="start">
@@ -67,13 +71,12 @@ export function SearchProviderMenu({
           }}
         >
           {enabledProviders.map((enabledProvider) => {
-            const Icon = PROVIDER_ICONS[enabledProvider]
             return (
               <DropdownMenuRadioItem
                 key={enabledProvider}
                 value={enabledProvider}
               >
-                <Icon aria-hidden="true" />
+                <ProviderIcon provider={enabledProvider} />
                 {PROVIDER_LABELS[enabledProvider]}
               </DropdownMenuRadioItem>
             )