feat(core): introduce Kind.Agent for sub-agent classification (#20369)

packages/core/src/agents/subagent-tool.test.ts

@@ -7,6 +7,7 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest';
 import { SubagentTool } from './subagent-tool.js';
 import { SubagentToolWrapper } from './subagent-tool-wrapper.js';
+import { Kind } from '../tools/tools.js';
 import type {
   LocalAgentDefinition,
   RemoteAgentDefinition,
@@ -70,6 +71,11 @@ describe('SubAgentInvocation', () => {
       .mockReturnValue(mockInnerInvocation);
   });
 
+  it('should have Kind.Agent', () => {
+    const tool = new SubagentTool(testDefinition, mockConfig, mockMessageBus);
+    expect(tool.kind).toBe(Kind.Agent);
+  });
+
   it('should delegate shouldConfirmExecute to the inner sub-invocation (local)', async () => {
     const tool = new SubagentTool(testDefinition, mockConfig, mockMessageBus);
     const params = {};