feat(ts): 实现 Polaris 可交互首页

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

ts/web/nextjs/polaris/src/features/home/lib/provider-preference.ts

@@ -0,0 +1,11 @@
+import { isSearchProvider } from "@/features/home/lib/search-providers"
+import type { SearchProvider } from "@/types/search"
+
+export const SEARCH_PROVIDER_STORAGE_KEY = "polaris.search.provider"
+
+export function parseStoredProvider(
+  value: string | null,
+  fallback: SearchProvider,
+): SearchProvider {
+  return isSearchProvider(value) ? value : fallback
+}