fix: 修复第三方 Anthropic base URL 应使用 ExaSearchAdapter 而非 BingSearchAdapter

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: claude-code-best

packages/builtin-tools/src/tools/WebSearchTool/adapters/index.ts

@@ -47,7 +47,7 @@ export function createAdapter(): WebSearchAdapter {
         ? 'bing'
         : isFirstPartyAnthropicBaseUrl()
           ? 'api'
-          : 'bing'
+          : 'exa'
 
   if (cachedAdapter && cachedAdapterKey === adapterKey) return cachedAdapter