AI search could not work together with MCP tools

- **Package Name**: azure-ai-agents
- **Package Version**: 1.2.0b3
- **Operating System**: Windows
- **Python Version**: 3.11.9

**Describe the bug**
AI search could not work when work with MCP tools. Below are the scenarios I tried.

1. Use AI search sample to create a new agent with AI search configured.
AI search tool works correctly

2. Use the same agent with AI search configured and pass MCP tools via AgentsClient.runs.stream().
MCP tools work correctly but AI search doesn't work

3. Use the same agent with AI search and pass MCP tools along with AI search tool via AgentsClient.runs.stream().
Both of MCP tools and AI search work correctly.

4. Use an agent without AI search configured and pass AI search tool via AgentsClient.runs.stream().
AI search doesn't work.

**To Reproduce**
Steps to reproduce the behavior:
See the above scenario descriptions.

**Expected behavior**
A clear and concise description of what you expected to happen.
If AI search is configured for an agent, it should also work when MCP tools are passed for a run.
If AI search is not configured for and agent, it should also work when pass AI search tool via AgentsClient.runs.stream().

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Additional context**
Add any other context about the problem here.

まず azure-ai-agents 1.2.0b3 で 4 つのシナリオを再現し、AgentsClient.runs.stream() と AI search と MCP tools の相互作用に重点を置きます。AI search が agent に設定されている場合と run に渡された場合の両方で機能し、MCP tools も受け取る run でも機能すれば完了です。

索引モデルが issue の本文から書いたものです。