Support M365 Agents SDK channel for Copilot Studio

Summary

Add support for connecting to Copilot Studio agents via the M365 Agents SDK channel, as an alternative to the current Direct Line channel.

Motivation

The M365 Agents SDK provides a newer protocol for communicating with Copilot Studio agents that supports:

• Streaming responses (token-by-token)
• Reasoning/thinking traces
• Citations and source references
• Generative search results
• Activity-based protocol with richer message types

This is the direction Microsoft is moving for Copilot Studio integrations and would provide a significantly richer chat experience compared to the current Direct Line approach.

Possible Approach

• Add a data-webchat-mode attribute (directline | m365)
• For M365 mode, require data-webchat-environment-id, data-webchat-agent-id, data-webchat-tenant-id, and data-webchat-client-id
• Authenticate with Microsoft using MSAL.js
• Use the M365 Agents SDK client to establish the conversation
• Render streaming responses, citations, and other rich content in the chat UI

Start by locating the embed configuration that handles data-webchat-mode and the existing Direct Line connection, then review how the chat UI renders messages. Define the M365 mode inputs, MSAL.js authentication, and M365 Agents SDK conversation flow; done means Copilot Studio connections support streaming responses, reasoning traces, citations, and other rich content.