[ai.agentserver] add azure-ai-agentserver-core package to agentserver

[lusu-msft]

Description

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• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
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Testing Guidelines

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[Copilot]

Pull Request Overview

This PR introduces a new Azure AI Agent Server Core package (azure-ai-agentserver-core) with comprehensive CI/CD setup, test infrastructure, sample applications, and core server implementation. The package provides a framework for building custom agent servers with support for streaming responses, OpenTelemetry tracing, and integration with Azure services.

Key Changes

• New agent server framework with FoundryCBAgent base class for custom agent implementations
• CI/CD pipeline configuration for automated testing and analysis
• Test infrastructure with fixtures for multiple sample scenarios (mock agents, MCP integration, bilingual planner)
• Sample applications demonstrating various agent patterns (mock agents, MCP tools, multi-agent workflows)

Reviewed Changes

Copilot reviewed 51 out of 53 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
sdk/agentserver/ci.yml	CI/CD pipeline configuration with triggers and test matrix
sdk/agentserver/tests.yml	Weekly analysis pipeline configuration
sdk/agentserver/platform-matrix.json	Platform test matrix with PortAudio requirement
sdk/agentserver/azure-ai-agentserver-core/tests/test_custom.py	Test suite for custom agent samples
sdk/agentserver/azure-ai-agentserver-core/tests/conftest.py	Pytest configuration with test client fixtures
sdk/agentserver/azure-ai-agentserver-core/tests/env-template	Environment variable documentation for tests
sdk/agentserver/azure-ai-agentserver-core/samples/*/	Sample implementations (mock, MCP, bilingual planner)
sdk/agentserver/azure-ai-agentserver-core/azure/ai/agentserver/core/server/base.py	Core server implementation with streaming support
sdk/agentserver/azure-ai-agentserver-core/azure/ai/agentserver/core/server/common/	Agent context and ID generation utilities
sdk/agentserver/azure-ai-agentserver-core/pyproject.toml	Package metadata and dependencies

Comments suppressed due to low confidence (2)

sdk/agentserver/ci.yml:1

• The ServiceDirectory parameter is set to ai but should be agentserver to match the actual service directory structure. This mismatch could cause the CI pipeline to look in the wrong directory for tests and artifacts.
  sdk/agentserver/azure-ai-agentserver-core/samples/bilingual_weekend_planner/main.py:1
• Corrected spelling of 'ANSII' to 'ANSI'. ANSI is the correct acronym for American National Standards Institute. The attack strategy should be ANSI_ATTACK.