Fix bearer token approach for Dotnet AF Sample

[Rahul Devikar (rahuldevikar761)]

No description provided.

[Copilot]

Pull request overview

This pull request refactors the authentication approach for non-agentic requests in the .NET Agent Framework sample. The changes remove the OBO (On-Behalf-Of) authentication handler ("me") and replace it with a bearer token-based approach for development and testing scenarios like Playground and WebChat.

Changes:

• Removed "me" authentication handler configuration from appsettings.json
• Simplified ToolingManifest.json to include only mcp_MailTools MCP server
• Added TryGetBearerTokenForDevelopment method to support bearer token authentication from environment variables
• Updated message handling logic to differentiate between agentic (uses auth handler) and non-agentic flows (uses bearer token)
• Changed error handling to gracefully continue without MCP tools instead of throwing exceptions

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 8 comments.

File	Description
dotnet/agent-framework/sample-agent/appsettings.json	Removed "me" MsalUserAuthorization handler configuration to align with new bearer token approach
dotnet/agent-framework/sample-agent/ToolingManifest.json	Reduced MCP servers from 7 to 1 (mcp_MailTools only), simplifying the sample configuration
dotnet/agent-framework/sample-agent/Agent/MyAgent.cs	Added bearer token support via environment variables, refactored authentication flow to handle agentic vs non-agentic requests differently, and improved error handling for graceful degradation