Add Claude (Anthropic SDK) sample agent for .NET

[Yogeshp-MSFT]

Adds a new .NET sample agent under dotnet/claude/sample-agent that uses Anthropic Claude as the LLM provider via the Anthropic.SDK NuGet package.

What this does

• Demonstrates using Anthropic.SDK 5.10.0 as an IChatClient drop-in replacement for Azure OpenAI, working seamlessly with ChatClientAgent and the Microsoft.Extensions.AI ecosystem.
• Follows the same architecture as dotnet/agent-framework/sample-agent — identical MCP tooling, agentic auth, observability, and hosting patterns.
• Includes streaming responses, typing indicators, multi-turn conversation sessions, file attachment handling, and prompt injection sanitization.

Key files

File	Purpose
Program.cs	Registers AnthropicClient as IChatClient with function invocation + OpenTelemetry
Agent/MyAgent.cs	Message handling, MCP tool loading, session management, observability
telemetry/	Full OpenTelemetry setup (metrics, tracing, A365 baggage) — mirrors reference sample
ToolingManifest.json	MCP server declarations (Mail)
Agent-Code-Walkthrough.md	Detailed code walkthrough

Package notes

Microsoft.Agents.AI is pinned to 1.0.0-rc4 — the last version compiled against Microsoft.Extensions.AI.Abstractions 10.3.0, which is binary-compatible with Anthropic.SDK 5.10.0. Newer versions (rc5+) target Abstractions 10.4.0+ and break at runtime due to removed HostedMcpServerTool.AuthorizationToken.

[Copilot]

Pull request overview

This PR adds a new .NET sample agent under dotnet/claude/sample-agent demonstrating how to use Anthropic Claude (via Anthropic.SDK) as an IChatClient in the Agent 365 / Microsoft 365 Agents hosting and tooling patterns.

Changes:

• Introduces a new Claude-based sample agent project (hosting, auth, MCP tooling, sessions, streaming UX).
• Adds OpenTelemetry setup plus custom agent metrics helpers/wrappers.
• Adds sample configuration, MCP ToolingManifest, and Teams app package artifacts.

Agent 365 Sample Validation Report (high-level)

• Documentation: README and code walkthrough are present.
• Configuration: appsettings.json and appsettings.Playground.json are present with placeholders (no obvious committed secrets).
• Project structure: .csproj, solution file, ToolingManifest, and Teams app package files are present.
• Issues found (require changes): telemetry wrappers do not correctly await async operations / mark failures; custom metrics likely not exported due to meter registration; attachment handling currently risks leaking tokenized file URLs to the LLM provider.

Reviewed changes

Copilot reviewed 17 out of 19 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
dotnet/claude/sample-agent/Tools/DateTimeFunctionTool.cs	Adds a local function tool for date/time.
dotnet/claude/sample-agent/ToolingManifest.json	Declares MCP server configuration (Mail tools).
dotnet/claude/sample-agent/telemetry/AgentOTELExtensions.cs	Adds OpenTelemetry configuration for the sample host.
dotnet/claude/sample-agent/telemetry/AgentMetrics.cs	Adds ActivitySource/Meter helpers and wrapper methods.
dotnet/claude/sample-agent/telemetry/A365OtelWrapper.cs	Adds A365 baggage/token-cache integration wrapper.
dotnet/claude/sample-agent/README.md	Documents the sample and key behaviors.
dotnet/claude/sample-agent/Program.cs	Configures DI, Anthropic IChatClient, routing, and endpoints.
dotnet/claude/sample-agent/m365agents.yml	Adds Teams toolkit metadata file.
dotnet/claude/sample-agent/m365agents.playground.yml	Adds Teams toolkit metadata for playground env usage.
dotnet/claude/sample-agent/ClaudeSampleAgent.csproj	New web project with A365 + Anthropic dependencies.
dotnet/claude/sample-agent/AspNetExtensions.cs	Adds JWT bearer token validation utilities for the host.
dotnet/claude/sample-agent/appsettings.Playground.json	Adds playground config (token validation disabled, placeholders).
dotnet/claude/sample-agent/appsettings.json	Adds default config (A365 options, connections, Anthropic settings).
dotnet/claude/sample-agent/appPackage/outline.png	Teams app icon asset.
dotnet/claude/sample-agent/appPackage/manifest.json	Teams app manifest for the sample agent.
dotnet/claude/sample-agent/appPackage/color.png	Teams app icon asset.
dotnet/claude/sample-agent/Agent/MyAgent.cs	Implements message handling, sessions, MCP tool loading, streaming UX.
dotnet/claude/sample-agent/Agent-Code-Walkthrough.md	Provides a detailed walkthrough of the sample’s code.
dotnet/claude/ClaudeSampleAgent.sln	Adds a solution file for the new sample.