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/query.ts

@@ -68,6 +68,9 @@ import {
 const skillPrefetch = feature('EXPERIMENTAL_SKILL_SEARCH')
   ? (require('./services/skillSearch/prefetch.js') as typeof import('./services/skillSearch/prefetch.js'))
   : null
+const toolSearchPrefetch = feature('EXPERIMENTAL_TOOL_SEARCH')
+  ? (require('./services/toolSearch/prefetch.js') as typeof import('./services/toolSearch/prefetch.js'))
+  : null
 const _jobClassifier = feature('TEMPLATES')
   ? (require('./jobs/classifier.js') as typeof import('./jobs/classifier.js'))
   : null
@@ -482,6 +485,10 @@ async function* queryLoop(
       messages,
       toolUseContext,
     )
+    const pendingToolPrefetch = toolSearchPrefetch?.startToolSearchPrefetch(
+      toolUseContext.options.tools ?? [],
+      messages,
+    )
 
     yield { type: 'stream_request_start' }
 
@@ -1917,6 +1924,17 @@ async function* queryLoop(
       }
     }
 
+    // Inject prefetched tool discovery.
+    if (toolSearchPrefetch && pendingToolPrefetch) {
+      const toolAttachments =
+        await toolSearchPrefetch.collectToolSearchPrefetch(pendingToolPrefetch)
+      for (const att of toolAttachments) {
+        const msg = createAttachmentMessage(att)
+        yield msg
+        toolResults.push(msg)
+      }
+    }
+
     // Remove only commands that were actually consumed as attachments.
     // Prompt and task-notification commands are converted to attachments above.
     const claimedCommandSet = new Set(claimedConsumedCommands)