feat(models): adding python support for Azure foundry models (OpenAI + Anthropic types)

[marosset]

Part of #2072

#2091 added foundry support for the Go runtime. This PR does the same for python.

As part of this change the AzureOpenAI model auth is moved to use unified Azure auth mechanisms (including API_KEY-less / workload identity support)

[Copilot]

Pull request overview

Adds Azure AI Foundry provider support to the Python ADK runtime, including OpenAI-compatible chat/embeddings and an Anthropic-format client path, while unifying Azure authentication to support API-key-less Azure Workload Identity via azure-identity.

Changes:

• Introduces shared Azure helpers (_azure.py) for endpoint/deployment resolution, auth header sanitization, and implicit Workload Identity token providers.
• Adds Foundry support to OpenAI chat and embeddings flows, plus Foundry Anthropic client support for Claude-on-Foundry.
• Expands unit test coverage for Azure OpenAI + Foundry auth modes (API key, passthrough, Workload Identity) and wiring.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
python/uv.lock	Adds Azure Identity dependency closure (azure-core, azure-identity, msal, msal-extensions).
python/packages/kagent-adk/pyproject.toml	Declares azure-identity as a runtime dependency for Workload Identity support.
python/packages/kagent-adk/src/kagent/adk/models/_azure.py	New shared Azure auth/config helpers and client builders for OpenAI + Anthropic surfaces.
python/packages/kagent-adk/src/kagent/adk/models/_openai.py	Refactors Azure OpenAI client creation to use unified Azure auth; adds Foundry OpenAI model support.
python/packages/kagent-adk/src/kagent/adk/models/_embedding.py	Adds Foundry embeddings provider path and unifies Azure embeddings client construction.
python/packages/kagent-adk/src/kagent/adk/models/_anthropic.py	Adds Foundry Anthropic implementation and improves passthrough client caching behavior.
python/packages/kagent-adk/src/kagent/adk/models/init.py	Exposes Foundry OpenAI model via public kagent.adk.models exports.
python/packages/kagent-adk/src/kagent/adk/types.py	Adds Foundry model config and wires provider dispatch (openai vs anthropic format).
python/packages/kagent-adk/tests/unittests/test_embedding.py	Adds Foundry embeddings tests for API key + Workload Identity + passthrough semantics.
python/packages/kagent-adk/tests/unittests/models/test_openai.py	Updates patch targets for Azure client construction; adds an import.
python/packages/kagent-adk/tests/unittests/models/test_azure.py	New tests validating Azure OpenAI/Foundry auth behavior and header sanitization.
python/packages/kagent-adk/tests/unittests/models/test_anthropic.py	Adds Foundry Anthropic tests (format dispatch, auth modes, request headers).

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[mesutoezdil]

forces 768 dims here too. same bug as _embed_openai above it, a fix for that one is already open in #2542. providers with other dims will fail here as well.