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/tools.ts

@@ -82,6 +82,7 @@ import { LSPTool } from '@claude-code-best/builtin-tools/tools/LSPTool/LSPTool.j
 import { ListMcpResourcesTool } from '@claude-code-best/builtin-tools/tools/ListMcpResourcesTool/ListMcpResourcesTool.js'
 import { ReadMcpResourceTool } from '@claude-code-best/builtin-tools/tools/ReadMcpResourceTool/ReadMcpResourceTool.js'
 import { ToolSearchTool } from '@claude-code-best/builtin-tools/tools/ToolSearchTool/ToolSearchTool.js'
+import { ExecuteTool } from '@claude-code-best/builtin-tools/tools/ExecuteTool/ExecuteTool.js'
 import { EnterPlanModeTool } from '@claude-code-best/builtin-tools/tools/EnterPlanModeTool/EnterPlanModeTool.js'
 import { EnterWorktreeTool } from '@claude-code-best/builtin-tools/tools/EnterWorktreeTool/EnterWorktreeTool.js'
 import { ExitWorktreeTool } from '@claude-code-best/builtin-tools/tools/ExitWorktreeTool/ExitWorktreeTool.js'
@@ -269,7 +270,7 @@ export function getAllBaseTools(): Tools {
     ReadMcpResourceTool,
     // Include ToolSearchTool when tool search might be enabled (optimistic check)
     // The actual decision to defer tools happens at request time in claude.ts
-    ...(isToolSearchEnabledOptimistic() ? [ToolSearchTool] : []),
+    ...(isToolSearchEnabledOptimistic() ? [ToolSearchTool, ExecuteTool] : []),
   ]
 }