feat: 实现 Tool Search 基础设施层（CORE_TOOLS 白名单 + TF-IDF 索引 + ExecuteTool + 搜索增强）

- 新增 CORE_TOOLS 白名单常量（31 个核心工具），重构 isDeferredTool 为白名单制判定
- 新建 TF-IDF 工具索引模块（toolIndex.ts），复用 localSearch.ts 算法函数
- 新建 ExecuteTool 跨 API provider 统一工具执行入口
- 增强 ToolSearchTool：TF-IDF 搜索路径、discover: 模式、并行搜索合并、文本模式回退
- 新增 27 个单元测试，precheck 零错误通过（4108 tests pass）

Co-Authored-By: glm-5.1[1m] <zai-org@claude-code-best.win>

src/screens/REPL.tsx

@@ -446,6 +446,8 @@ import { useLspPluginRecommendation } from 'src/hooks/useLspPluginRecommendation
 import { LspRecommendationMenu } from 'src/components/LspRecommendation/LspRecommendationMenu.js';
 import { useClaudeCodeHintRecommendation } from 'src/hooks/useClaudeCodeHintRecommendation.js';
 import { PluginHintMenu } from 'src/components/ClaudeCodeHint/PluginHintMenu.js';
+import { ToolSearchHint } from 'src/components/ToolSearchHint.js';
+import { useToolSearchHint } from 'src/hooks/useToolSearchHint.js';
 import {
   DesktopUpsellStartup,
   shouldShowDesktopUpsellStartup,
@@ -1036,6 +1038,7 @@ export function REPL({
   useTeammateLifecycleNotification();
   const { recommendation: lspRecommendation, handleResponse: handleLspResponse } = useLspPluginRecommendation();
   const { recommendation: hintRecommendation, handleResponse: handleHintResponse } = useClaudeCodeHintRecommendation();
+  const toolSearchHint = useToolSearchHint();
 
   // Memoize the combined initial tools array to prevent reference changes
   const combinedInitialTools = useMemo(() => {
@@ -2391,6 +2394,7 @@ export function REPL({
     | 'remote-callout'
     | 'lsp-recommendation'
     | 'plugin-hint'
+    | 'tool-search-hint'
     | 'desktop-upsell'
     | 'ultraplan-choice'
     | 'ultraplan-launch'
@@ -2445,6 +2449,9 @@ export function REPL({
     // Plugin hint from CLI/SDK stderr (same priority band as LSP rec)
     if (allowDialogsWithAnimation && hintRecommendation) return 'plugin-hint';
 
+    // Tool search hint (discovered tools relevant to current query)
+    if (allowDialogsWithAnimation && toolSearchHint.visible) return 'tool-search-hint';
+
     // Desktop app upsell (max 3 launches, lowest priority)
     if (allowDialogsWithAnimation && showDesktopUpsellStartup) return 'desktop-upsell';
 
@@ -6173,6 +6180,14 @@ export function REPL({
                   />
                 )}
 
+                {focusedInputDialog === 'tool-search-hint' && toolSearchHint.visible && (
+                  <ToolSearchHint
+                    tools={toolSearchHint.tools}
+                    onSelect={toolSearchHint.handleSelect}
+                    onDismiss={toolSearchHint.handleDismiss}
+                  />
+                )}
+
                 {focusedInputDialog === 'lsp-recommendation' && lspRecommendation && (
                   <LspRecommendationMenu
                     pluginName={lspRecommendation.pluginName}