fix: 修复 Tool Search 缓存失效 — deferred 工具不再动态注入 tools 数组

移除 deferred 工具的 "discover then include" 逻辑，让 tools 数组在整个会话中
保持稳定（只有 core tools + ToolSearch + ExecuteExtraTool），避免每次发现新
工具时 tools JSON 变化导致 prompt cache 失效。

同时强化工具优先级引导：core tools 优先直接调用，ToolSearch/ExecuteExtraTool
仅作为发现和调用 deferred 工具的最后手段。当模型搜索已加载的 core tool 时，
ToolSearch 返回明确的拒绝提示。

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

src/services/api/openai/index.ts

@@ -53,7 +53,6 @@ import {
 import type { SDKAssistantMessageError } from '../../../entrypoints/agentSdkTypes.js'
 import {
   isToolSearchEnabled,
-  extractDiscoveredToolNames,
   isDeferredToolsDeltaEnabled,
 } from '../../../utils/toolSearch.js'
 import {
@@ -213,17 +212,18 @@ export async function* queryModelOpenAI(
     }
 
     // 5. Filter tools (similar to Anthropic path)
+    // Never include deferred tools in the API tools array — they are invoked
+    // via ExecuteExtraTool which looks them up from the global tool registry
+    // at runtime. Keeping the tools array stable preserves the prompt cache.
     let filteredTools = tools
     if (useToolSearch && deferredToolNames.size > 0) {
-      const discoveredToolNames = extractDiscoveredToolNames(messages)
-
       filteredTools = tools.filter(tool => {
         // Always include non-deferred tools
         if (!deferredToolNames.has(tool.name)) return true
         // Always include ToolSearchTool (so it can discover more tools)
         if (toolMatchesName(tool, TOOL_SEARCH_TOOL_NAME)) return true
-        // Only include deferred tools that have been discovered
-        return discoveredToolNames.has(tool.name)
+        // All other deferred tools are excluded — use ExecuteExtraTool instead
+        return false
       })
     }