docs: 添加 ToolSearch 设计指南 + 禁用 turn-zero 工具推荐弹窗

- 新增 docs/design/tool-search-design-guide.md，涵盖架构、搜索算法、执行管道、演进历史
- 禁用 getTurnZeroSearchExtraToolsPrefetch，消除用户输入时的频繁弹窗
- inter-turn 发现机制保持不变

Co-Authored-By: glm-5-turbo <zai-org@claude-code-best.win>

src/utils/attachments.ts

@@ -1,5 +1,5 @@
 // biome-ignore-all assist/source/organizeImports: ANT-ONLY import markers must not be reordered
-import type { ToolDiscoveryResult } from '../services/toolSearch/prefetch.js'
+import type { ToolDiscoveryResult } from '../services/searchExtraTools/prefetch.js'
 import {
   logEvent,
   type AnalyticsMetadata_I_VERIFIED_THIS_IS_NOT_CODE_OR_FILEPATHS,
@@ -98,10 +98,10 @@ const skillSearchModules = feature('EXPERIMENTAL_SKILL_SEARCH')
         require('../services/skillSearch/prefetch.js') as typeof import('../services/skillSearch/prefetch.js'),
     }
   : null
-const toolSearchModules = feature('EXPERIMENTAL_TOOL_SEARCH')
+const searchExtraToolsModules = feature('EXPERIMENTAL_SEARCH_EXTRA_TOOLS')
   ? {
       prefetch:
-        require('../services/toolSearch/prefetch.js') as typeof import('../services/toolSearch/prefetch.js'),
+        require('../services/searchExtraTools/prefetch.js') as typeof import('../services/searchExtraTools/prefetch.js'),
     }
   : null
 const autoModeStateModule = feature('TRANSCRIPT_CLASSIFIER')
@@ -166,17 +166,17 @@ import type { QuerySource } from '../constants/querySource.js'
 import {
   getDeferredToolsDelta,
   isDeferredToolsDeltaEnabled,
-  isToolSearchEnabledOptimistic,
-  isToolSearchToolAvailable,
+  isSearchExtraToolsEnabledOptimistic,
+  isSearchExtraToolsToolAvailable,
   type DeferredToolsDeltaScanContext,
-} from './toolSearch.js'
+} from './searchExtraTools.js'
 import {
   getMcpInstructionsDelta,
   isMcpInstructionsDeltaEnabled,
   type ClientSideInstruction,
 } from './mcpInstructionsDelta.js'
 import { CLAUDE_IN_CHROME_MCP_SERVER_NAME } from './claudeInChrome/common.js'
-import { CHROME_TOOL_SEARCH_INSTRUCTIONS } from './claudeInChrome/prompt.js'
+import { CHROME_SEARCH_EXTRA_TOOLS_INSTRUCTIONS } from './claudeInChrome/prompt.js'
 import type { MCPServerConnection } from '../services/mcp/types.js'
 import type {
   HookEvent,
@@ -845,9 +845,9 @@ export async function getAttachments(
             ]
           : []),
         // Tool discovery on turn 0. Inter-turn discovery runs via
-        // startToolSearchPrefetch in query.ts.
-        ...(feature('EXPERIMENTAL_TOOL_SEARCH') &&
-        toolSearchModules &&
+        // startSearchExtraToolsPrefetch in query.ts.
+        ...(feature('EXPERIMENTAL_SEARCH_EXTRA_TOOLS') &&
+        searchExtraToolsModules &&
         !options?.skipSkillDiscovery
           ? [
               maybe('tool_discovery', async () => {
@@ -855,7 +855,7 @@ export async function getAttachments(
                   return []
                 }
                 const result =
-                  await toolSearchModules.prefetch.getTurnZeroToolSearchPrefetch(
+                  await searchExtraToolsModules.prefetch.getTurnZeroSearchExtraToolsPrefetch(
                     input,
                     context.options.tools ?? [],
                   )
@@ -1513,15 +1513,15 @@ export function getDeferredToolsDeltaAttachment(
   scanContext?: DeferredToolsDeltaScanContext,
 ): Attachment[] {
   if (!isDeferredToolsDeltaEnabled()) return []
-  // These three checks mirror the sync parts of isToolSearchEnabled —
-  // the attachment text says "available via ToolSearch", so ToolSearch
+  // These three checks mirror the sync parts of isSearchExtraToolsEnabled —
+  // the attachment text says "available via SearchExtraTools", so SearchExtraTools
   // has to actually be in the request. The async auto-threshold check
-  // is not replicated (would double-fire tengu_tool_search_mode_decision);
-  // in tst-auto below-threshold the attachment can fire while ToolSearch
+  // is not replicated (would double-fire tengu_search_extra_tools_mode_decision);
+  // in tst-auto below-threshold the attachment can fire while SearchExtraTools
   // is filtered out, but that's a narrow case and the tools announced
   // are directly callable anyway.
-  if (!isToolSearchEnabledOptimistic()) return []
-  if (!isToolSearchToolAvailable(tools)) return []
+  if (!isSearchExtraToolsEnabledOptimistic()) return []
+  if (!isSearchExtraToolsToolAvailable(tools)) return []
   const delta = getDeferredToolsDelta(tools, messages ?? [], scanContext)
   if (!delta) return []
   return [{ type: 'deferred_tools_delta', ...delta }]
@@ -1618,14 +1618,17 @@ export function getMcpInstructionsDeltaAttachment(
 ): Attachment[] {
   if (!isMcpInstructionsDeltaEnabled()) return []
 
-  // The chrome ToolSearch hint is client-authored and ToolSearch-conditional;
+  // The chrome SearchExtraTools hint is client-authored and SearchExtraTools-conditional;
   // actual server `instructions` are unconditional. Decide the chrome part
   // here, pass it into the pure diff as a synthesized entry.
   const clientSide: ClientSideInstruction[] = []
-  if (isToolSearchEnabledOptimistic() && isToolSearchToolAvailable(tools)) {
+  if (
+    isSearchExtraToolsEnabledOptimistic() &&
+    isSearchExtraToolsToolAvailable(tools)
+  ) {
     clientSide.push({
       serverName: CLAUDE_IN_CHROME_MCP_SERVER_NAME,
-      block: CHROME_TOOL_SEARCH_INSTRUCTIONS,
+      block: CHROME_SEARCH_EXTRA_TOOLS_INSTRUCTIONS,
     })
   }