chore: import upstream snapshot with attribution

showcase/integrations/ms-agent-harness-dotnet/.env.example

@@ -0,0 +1,40 @@
+# =============================================================================
+# Agent backend (.NET, agent/Program.cs)
+# =============================================================================
+
+# OpenAI-compatible API key used by the .NET agent.
+# Precedence: OPENAI_API_KEY > GitHubToken > "sk-mock-local" (mock fallback).
+# Set OPENAI_API_KEY for production OpenAI/Azure usage.
+OPENAI_API_KEY=
+
+# GitHub token for accessing GitHub Models (Azure AI inference endpoint).
+# Used as a fallback API key when OPENAI_API_KEY is not set.
+# Get via: gh auth token
+# Format: ghp_...
+GitHubToken=
+
+# Optional. Override the OpenAI-compatible base URL (e.g. when pointing at
+# aimock, a self-hosted gateway, or Azure AI inference).
+# Defaults to https://models.inference.ai.azure.com when unset.
+# OPENAI_BASE_URL=
+
+# =============================================================================
+# Next.js frontend (src/app/api/*)
+# =============================================================================
+
+# URL the CopilotKit runtime proxy uses to reach the .NET agent backend.
+# Inside the container this is localhost:8000; in dev set to wherever the
+# `dotnet run` process is listening.
+AGENT_URL=http://localhost:8000
+
+# Public base URL of the Next.js app — used by the smoke endpoint to build
+# absolute URLs back to itself.
+NEXT_PUBLIC_BASE_URL=http://localhost:3000
+
+# Optional. MCP server URL forwarded to CopilotKit's MCP integration.
+# Defaults to https://mcp.excalidraw.com when unset.
+# MCP_SERVER_URL=
+
+# Optional. Bearer token required by /api/debug. When unset the debug route
+# is effectively disabled.
+# SHOWCASE_DEBUG_TOKEN=