Python: [BREAKING] Python: Provider-leading client design & OpenAI package extraction (#4818)

* Python: Provider-leading client design & OpenAI package extraction

Major refactoring of the Python Agent Framework client architecture:

- Extract OpenAI clients into new `agent-framework-openai` package
- Core package no longer depends on openai, azure-identity, azure-ai-projects
- Rename clients for discoverability: OpenAIResponsesClient → OpenAIChatClient,
  OpenAIChatClient → OpenAIChatCompletionClient
- Unify `model_id`/`deployment_name`/`model_deployment_name` → `model` param
- New FoundryChatClient for Azure AI Foundry Responses API
- New FoundryAgent/FoundryAgentClient for connecting to pre-configured Foundry agents
- Remove OpenAIBase/OpenAIConfigMixin from non-deprecated client MRO
- Deprecate AzureOpenAI* clients, AzureAIClient, OpenAIAssistantsClient
- Reorganize samples: azure_openai+azure_ai+azure_ai_agent → azure/
- ADR-0020: Provider-Leading Client Design

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: missing Agent imports in samples, .model_id → .model in foundry_local sample

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: CI failures — mypy errors, coverage targets, sample imports

- azure-ai mypy: add type ignores for TypedDict total=, model arg, forward ref
- Coverage: replace core.azure/openai targets with openai package target
- project_provider: add type annotation for opts dict

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: populate openai .pyi stub, fix broken README links, coverage targets

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fixes

* updated observabilitty

* reset azure init.pyi

* fix errors

* updated adr number

* fix foundry local

* fixed not renamed docstrings and comments, and added deprecated markers to old classes

* fix tests and pyprojects

* fix test vars

* updated function tests

* update durable

* updated test setup for functions

* Fix Foundry auth in workflow samples

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Stabilize Python integration workflows

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Update hosting samples for Foundry

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Trigger full CI rerun

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Trigger CI rerun again

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* trigger rerun

* trigger rerun

* fix for litellm

* undo durabletask changes

* Move Foundry APIs into foundry namespace

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Fix Foundry pyproject formatting

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Split provider samples by Foundry surface

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Restore hosting sample requirements

Also fix the Foundry Local sample link after the provider sample move.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* updated tests

* udpated foundry integration tests

* removed dist from azurefunctions tests

* Use separate Foundry clients for concurrent agents

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix client setup in azfunc and durable

* disabled two tests

* updated setup for some function and durable tests

* improved azure openai setup with new clients

* ignore deprecated

* fixes

* skip 11

* remove openai assistants int tests

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

python/packages/foundry/tests/conftest.py

@@ -0,0 +1,78 @@
+# Copyright (c) Microsoft. All rights reserved.
+from typing import Any
+from unittest.mock import AsyncMock, MagicMock
+
+from pytest import fixture
+
+
+@fixture
+def exclude_list(request: Any) -> list[str]:
+    """Fixture that returns a list of environment variables to exclude."""
+    return request.param if hasattr(request, "param") else []
+
+
+@fixture
+def override_env_param_dict(request: Any) -> dict[str, str]:
+    """Fixture that returns a dict of environment variables to override."""
+    return request.param if hasattr(request, "param") else {}
+
+
+@fixture()
+def foundry_unit_test_env(monkeypatch, exclude_list, override_env_param_dict):  # type: ignore
+    """Fixture to set environment variables for Foundry settings."""
+
+    if exclude_list is None:
+        exclude_list = []
+
+    if override_env_param_dict is None:
+        override_env_param_dict = {}
+
+    env_vars = {
+        "FOUNDRY_PROJECT_ENDPOINT": "https://test-project.services.ai.azure.com/",
+        "FOUNDRY_MODEL": "test-gpt-4o",
+    }
+
+    env_vars.update(override_env_param_dict)  # type: ignore
+
+    for key, value in env_vars.items():
+        if key in exclude_list:
+            monkeypatch.delenv(key, raising=False)  # type: ignore
+            continue
+        monkeypatch.setenv(key, value)  # type: ignore
+
+    return env_vars
+
+
+@fixture
+def mock_agents_client() -> MagicMock:
+    """Fixture that provides a mock AgentsClient."""
+    mock_client = MagicMock()
+
+    # Mock agents property
+    mock_client.create_agent = AsyncMock()
+    mock_client.delete_agent = AsyncMock()
+
+    # Mock agent creation response
+    mock_agent = MagicMock()
+    mock_agent.id = "test-agent-id"
+    mock_client.create_agent.return_value = mock_agent
+
+    # Mock threads property
+    mock_client.threads = MagicMock()
+    mock_client.threads.create = AsyncMock()
+    mock_client.messages.create = AsyncMock()
+
+    # Mock runs property
+    mock_client.runs = MagicMock()
+    mock_client.runs.list = AsyncMock()
+    mock_client.runs.cancel = AsyncMock()
+    mock_client.runs.stream = AsyncMock()
+    mock_client.runs.submit_tool_outputs_stream = AsyncMock()
+
+    return mock_client
+
+
+@fixture
+def mock_azure_credential() -> MagicMock:
+    """Fixture that provides a mock AsyncTokenCredential."""
+    return MagicMock()