feat: 重构 WebSearch/WebFetch，新增 Tavily 适配器及 /web-tools 面板

- WebSearch: 默认 Tavily，适配器优先级 WEB_SEARCH_ADAPTER > settings.webSearchAdapter > tavily
- WebFetch: 支持 Tavily /extract 返回 Markdown，移除 domain blacklist 远程检查
- 新增 /web-tools 命令面板（Search/Fetch 双 Tab + 二级配置菜单）
- 新增 settings 字段: webSearchAdapter, webFetchAdapter, tavilyEndpointUrl, braveApiKey, exaApiKey, exaEndpointUrl, webFetchHttpTimeoutMs
- 适配器联动: Tavily/Exa 从 settings 读取 endpoint 和 API key

Co-Authored-By: deepseek-v4-pro <deepseek-ai@claude-code-best.win>

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

@@ -0,0 +1,94 @@
+/**
+ * Tavily-based search adapter — calls the Tavily Search API
+ * (https://tavily.claude-code-best.win) and maps results to
+ * the unified SearchResult format.
+ */
+
+import axios from 'axios'
+import { AbortError } from 'src/utils/errors.js'
+import { getSettings_DEPRECATED } from 'src/utils/settings/settings.js'
+import type { SearchResult, SearchOptions, WebSearchAdapter } from './types.js'
+
+const DEFAULT_TAVILY_SEARCH_URL = 'https://tavily.claude-code-best.win/search'
+const FETCH_TIMEOUT_MS = 30_000
+
+interface TavilySearchHit {
+  title: string
+  url: string
+  content: string
+  score: number
+}
+
+interface TavilySearchResponse {
+  results: TavilySearchHit[]
+}
+
+export class TavilySearchAdapter implements WebSearchAdapter {
+  async search(query: string, options: SearchOptions): Promise<SearchResult[]> {
+    const { signal, onProgress, allowedDomains, blockedDomains } = options
+
+    if (signal?.aborted) {
+      throw new AbortError()
+    }
+
+    onProgress?.({ type: 'query_update', query })
+
+    const abortController = new AbortController()
+    if (signal) {
+      signal.addEventListener('abort', () => abortController.abort(), {
+        once: true,
+      })
+    }
+
+    const settings = getSettings_DEPRECATED() as Record<string, unknown> & {
+      tavilyEndpointUrl?: string
+    }
+    const searchUrl = settings.tavilyEndpointUrl || DEFAULT_TAVILY_SEARCH_URL
+
+    try {
+      const response = await axios.post<{
+        query: string
+        results: TavilySearchHit[]
+      }>(
+        searchUrl,
+        {
+          query,
+          search_depth: 'basic',
+          max_results: options.numResults ?? 8,
+          include_domains: allowedDomains ?? [],
+          exclude_domains: blockedDomains ?? [],
+        },
+        {
+          signal: abortController.signal,
+          timeout: FETCH_TIMEOUT_MS,
+          headers: { 'Content-Type': 'application/json' },
+        },
+      )
+
+      if (abortController.signal.aborted) {
+        throw new AbortError()
+      }
+
+      const results: SearchResult[] = (response.data.results ?? []).map(
+        (hit: TavilySearchHit) => ({
+          title: hit.title,
+          url: hit.url,
+          snippet: hit.content,
+        }),
+      )
+
+      onProgress?.({
+        type: 'search_results_received',
+        resultCount: results.length,
+        query,
+      })
+
+      return results
+    } catch (e) {
+      if (axios.isCancel(e) || abortController.signal.aborted) {
+        throw new AbortError()
+      }
+      throw e
+    }
+  }
+}