The SDK's Agent type definition was missing the `title` field, causing
TypeScript errors when accessing item.title in the agent dialog component.
**Changes:**
- Added optional `title?: string` field to Agent type in SDK
This aligns the SDK type with the config schema definition where
title was already added.
Fixes typecheck failure in PR #13839
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>