Python: [BREAKING] Remove deprecated Python OpenAI/Azure AI surfaces (#4990)

* [BREAKING] Remove deprecated Python OpenAI/Azure AI surfaces

Also clean up follow-on docs, environment guidance, package metadata, and lab test stability.

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

* Fix deleted semantic-kernel sample links

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

* Address PR review feedback

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

* improve foundry language

* Fix A2A Foundry sample regression

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

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

python/CODING_STANDARD.md

@@ -192,7 +192,7 @@ The package follows a flat import structure:
 - **Connectors**: Import from `agent_framework.<vendor/platform>`
   ```python
   from agent_framework.openai import OpenAIChatClient
-  from agent_framework.azure import AzureOpenAIChatClient
+  from agent_framework.foundry import FoundryChatClient
   ```
 
 ## Exception Hierarchy
@@ -429,6 +429,10 @@ Each file should have a single first line containing: # Copyright (c) Microsoft.
 We follow the [Google Docstring](https://github.com/google/styleguide/blob/gh-pages/pyguide.md#383-functions-and-methods) style guide for functions and methods.
 They are currently not checked for private functions (functions starting with '_').
 
+When a change adds, removes, or renames a sample-facing environment variable in repo-level samples or
+package-local sample docs for a package included by `agent-framework-core[all]`, update the consolidated
+inventory in `samples/README.md` in the same change.
+
 They should contain:
 
 - Single line explaining what the function does, ending with a period.