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/utils/toolSearch.ts

@@ -449,13 +449,14 @@ function isToolResultBlockWithStringContent(
 
 /**
  * Regex to extract tool names from ToolSearchTool text output.
- * Matches: "Found N deferred tool(s): ToolA, ToolB."
+ * Matches: "Found N deferred tool(s): ToolA, mcp.server.ToolB."
+ * Uses multiline + end-of-line anchor so dots inside tool names (e.g. mcp__s__t) don't break parsing.
  */
-const DISCOVERED_TOOLS_PATTERN = /Found \d+ deferred tool\(s\): ([^.]+)\./
+const DISCOVERED_TOOLS_PATTERN = /^Found \d+ deferred tool\(s\): (.+)\.$/m
 
 /**
  * Extract tool names from ToolSearchTool text output.
- * Format: "Found N deferred tool(s): ToolA, ToolB. ..."
+ * Format: "Found N deferred tool(s): ToolA, ToolB.\n..."
  */
 function extractToolNamesFromText(text: string): string[] {
   const match = DISCOVERED_TOOLS_PATTERN.exec(text)
@@ -501,6 +502,18 @@ export function extractDiscoveredToolNames(messages: Message[]): Set<string> {
       continue
     }
 
+    // Deferred-tools-delta attachments announce tools that the model should
+    // see as available. Include their addedNames so the filter in claude.ts
+    // keeps the corresponding tool schemas in the API request.
+    if (
+      msg.type === 'attachment' &&
+      (msg as any).attachment?.type === 'deferred_tools_delta'
+    ) {
+      const added: string[] = (msg as any).attachment.addedNames ?? []
+      for (const name of added) discoveredTools.add(name)
+      continue
+    }
+
     // Only user messages contain tool_result blocks (responses to tool_use)
     if (msg.type !== 'user') continue