Python: Allow AzureOpenAIResponsesClient creation with Foundry project endpoint (#3814)

* Initial plan

* feat: extend AzureOpenAIResponsesClient to support Foundry project endpoints

Add project_client and project_endpoint parameters to allow creating
the client via an Azure AI Foundry project. When provided, the client
uses AIProjectClient.get_openai_client() to obtain the OpenAI client.
The azure-ai-projects package is imported lazily and only required
when using the project endpoint path.

Co-authored-by: eavanvalkenburg <13749212+eavanvalkenburg@users.noreply.github.com>

* fix: address code review - remove duplicate MagicMock imports in tests

Co-authored-by: eavanvalkenburg <13749212+eavanvalkenburg@users.noreply.github.com>

* fix: add type field to Responses API input items and add Foundry sample

- Add 'type: message' to input items in _prepare_message_for_openai
  to comply with the Responses API schema requirement
- Filter out empty dicts from unsupported content types to prevent
  sending items with invalid empty type values
- Add azure_responses_client_with_foundry.py sample demonstrating
  AzureOpenAIResponsesClient with project_endpoint
- Update README and pyrightconfig.samples.json accordingly

* updates to response format and setup

* fix: patch AIProjectClient at correct module path in test

Patch agent_framework.azure._responses_client.AIProjectClient instead of
azure.ai.projects.aio.AIProjectClient since the import is at module level.

* docs: add Foundry sample to READMEs and document AZURE_AI_PROJECT_ENDPOINT env var

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eavanvalkenburg <13749212+eavanvalkenburg@users.noreply.github.com>
Co-authored-by: eavanvalkenburg <github@vanvalkenburg.eu>

python/uv.lock

@@ -209,7 +209,6 @@ dependencies = [
     { name = "agent-framework-core", marker = "sys_platform == 'darwin' or sys_platform == 'linux' or sys_platform == 'win32'" },
     { name = "aiohttp", marker = "sys_platform == 'darwin' or sys_platform == 'linux' or sys_platform == 'win32'" },
     { name = "azure-ai-agents", marker = "sys_platform == 'darwin' or sys_platform == 'linux' or sys_platform == 'win32'" },
-    { name = "azure-ai-projects", marker = "sys_platform == 'darwin' or sys_platform == 'linux' or sys_platform == 'win32'" },
 ]
 
 [package.metadata]
@@ -217,7 +216,6 @@ requires-dist = [
     { name = "agent-framework-core", editable = "packages/core" },
     { name = "aiohttp" },
     { name = "azure-ai-agents", specifier = "==1.2.0b5" },
-    { name = "azure-ai-projects", specifier = ">=2.0.0b3" },
 ]
 
 [[package]]
@@ -324,6 +322,7 @@ name = "agent-framework-core"
 version = "1.0.0b260210"
 source = { editable = "packages/core" }
 dependencies = [
+    { name = "azure-ai-projects", marker = "sys_platform == 'darwin' or sys_platform == 'linux' or sys_platform == 'win32'" },
     { name = "azure-identity", marker = "sys_platform == 'darwin' or sys_platform == 'linux' or sys_platform == 'win32'" },
     { name = "mcp", extra = ["ws"], marker = "sys_platform == 'darwin' or sys_platform == 'linux' or sys_platform == 'win32'" },
     { name = "openai", marker = "sys_platform == 'darwin' or sys_platform == 'linux' or sys_platform == 'win32'" },
@@ -378,6 +377,7 @@ requires-dist = [
     { name = "agent-framework-orchestrations", marker = "extra == 'all'", editable = "packages/orchestrations" },
     { name = "agent-framework-purview", marker = "extra == 'all'", editable = "packages/purview" },
     { name = "agent-framework-redis", marker = "extra == 'all'", editable = "packages/redis" },
+    { name = "azure-ai-projects", specifier = ">=2.0.0b3" },
     { name = "azure-identity", specifier = ">=1,<2" },
     { name = "mcp", extras = ["ws"], specifier = ">=1.24.0,<2" },
     { name = "openai", specifier = ">=1.99.0" },