Add agent-with-hosted-mcp sample to hosted agents (Python)

[Copilot]

The samples/python/hosted-agents/agent-framework/ directory was missing an MCP sample equivalent to samples-classic/python/getting-started-agents/agent-framework/agent_with_hosted_mcp.

New sample: agent-with-hosted-mcp

• main.py — HostedMCPTool wired to https://learn.microsoft.com/api/mcp via AzureOpenAIChatClient + DefaultAzureCredential
• agent.yaml — hosted agent config; AZURE_OPENAI_ENDPOINT / AZURE_OPENAI_CHAT_DEPLOYMENT_NAME env vars, gpt-4o-mini model resource
• Dockerfile — Python 3.12-slim, matches sibling samples
• requirements.txt — azure-ai-agentserver-agentframework==1.0.0b12
• README.md — prerequisites, env setup, local run, deployment pointer

agent = AzureOpenAIChatClient(credential=DefaultAzureCredential()).create_agent(
    name="DocsAgent",
    instructions="You are a helpful assistant that can help with microsoft documentation questions.",
    tools=[HostedMCPTool(name="Microsoft Learn MCP", url="https://learn.microsoft.com/api/mcp")],
)
from_agent_framework(agent).run()

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