Python: Update workflow orchestration samples to use AzureOpenAIResponsesClient

[moonbox3]

Motivation and Context

• Restore AzureOpenAIResponsesClient usage across 13 orchestration samples and 1 declarative sample that were reverted to AzureOpenAIChatClient/OpenAIChatClient by Python / .NET Samples - Restructure and Improve Samples (Feature Branc… #4092 originally completed in Python: (samples): adopt AzureOpenAIResponsesClient, reorganize orchestration examples, and fix workflow/orchestration bugs #3873
• Update docstrings, type annotations, and prerequisites to match
• Add README sections explaining why orchestrations use AzureOpenAIResponsesClient (lightweight Responses API) vs the CRUD-style AzureAIAgent client

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

This pull request restores the use of AzureOpenAIResponsesClient across 13 orchestration samples and 1 declarative sample that were previously reverted to use AzureOpenAIChatClient/OpenAIChatClient by PR #4092. The changes align these samples with the recommended client for orchestration patterns that create agents locally without requiring server-side lifecycle management.

Changes:

• Updated all affected samples to use AzureOpenAIResponsesClient with project_endpoint and deployment_name parameters
• Added comprehensive README sections explaining why orchestrations use AzureOpenAIResponsesClient over the CRUD-style AzureAIAgent client
• Fixed a private import issue in magentic_checkpoint.py (changed from azure.identity._credentials to azure.identity)

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
python/samples/03-workflows/orchestrations/sequential_custom_executors.py	Restored AzureOpenAIResponsesClient with project_endpoint initialization
python/samples/03-workflows/orchestrations/sequential_agents.py	Restored AzureOpenAIResponsesClient with project_endpoint initialization
python/samples/03-workflows/orchestrations/magentic_human_plan_review.py	Restored AzureOpenAIResponsesClient, removed OpenAIChatClient usage
python/samples/03-workflows/orchestrations/magentic_checkpoint.py	Restored AzureOpenAIResponsesClient, fixed private import from azure.identity._credentials
python/samples/03-workflows/orchestrations/magentic.py	Restored AzureOpenAIResponsesClient, removed OpenAIChatClient and OpenAIResponsesClient usage
python/samples/03-workflows/orchestrations/handoff_simple.py	Restored AzureOpenAIResponsesClient with updated type annotations and docstrings
python/samples/03-workflows/orchestrations/handoff_autonomous.py	Restored AzureOpenAIResponsesClient with updated type annotations
python/samples/03-workflows/orchestrations/group_chat_simple_selector.py	Restored AzureOpenAIResponsesClient with project_endpoint initialization
python/samples/03-workflows/orchestrations/group_chat_philosophical_debate.py	Restored AzureOpenAIResponsesClient in helper function
python/samples/03-workflows/orchestrations/group_chat_agent_manager.py	Restored AzureOpenAIResponsesClient with project_endpoint initialization
python/samples/03-workflows/orchestrations/concurrent_custom_aggregator.py	Restored AzureOpenAIResponsesClient, updated docstring references
python/samples/03-workflows/orchestrations/concurrent_custom_agent_executors.py	Restored AzureOpenAIResponsesClient with updated type annotations and docstrings
python/samples/03-workflows/orchestrations/concurrent_agents.py	Restored AzureOpenAIResponsesClient, updated code comments
python/samples/03-workflows/orchestrations/README.md	Added "Why AzureOpenAIResponsesClient?" section explaining the choice and environment variables
python/samples/03-workflows/declarative/function_tools/README.md	Updated code example to use AzureOpenAIResponsesClient
python/samples/03-workflows/declarative/agent_to_function_tool/main.py	Restored AzureOpenAIResponsesClient with project_endpoint initialization
python/samples/03-workflows/README.md	Added "AzureOpenAIResponsesClient vs AzureAIAgent" section with detailed comparison