[3/8] Run Python SDK tests in CI

[aibrahim-oai]

Why

The Python SDK stack now depends on packaging metadata, pinned runtime wheels, generated artifacts, async behavior, and stream interleaving. Those checks need to run in CI so future changes cannot bypass the SDK test suite.

What

• Add a dedicated python-sdk job to .github/workflows/sdk.yml.
• Run the job in python:3.12-alpine so dependency resolution exercises the pinned musl runtime wheel.
• Keep the Python SDK test job parallel to the existing SDK job instead of serializing the full workflow.

Stack

1. [1/8] Pin Python SDK runtime dependency #21891 [1/8] Pin Python SDK runtime dependency
2. [2/8] Generate Python SDK types from pinned runtime #21893 [2/8] Generate Python SDK types from pinned runtime
3. This PR [3/8] Run Python SDK tests in CI
4. [4/8] Define Python SDK public API surface #21896 [4/8] Define Python SDK public API surface
5. [5/8] Rename Python SDK package to openai-codex #21905 [5/8] Rename Python SDK package to openai-codex
6. [6/8] Add high-level Python SDK approval mode #21910 [6/8] Add high-level Python SDK approval mode
7. [7/8] Add Python SDK app-server integration harness #22014 [7/8] Add Python SDK app-server integration harness
8. [8/8] Add Python SDK Ruff formatting #22021 [8/8] Add Python SDK Ruff formatting

Verification

• The added workflow job installs the SDK with uv sync --extra dev --frozen and runs the Python SDK pytest suite.

[aibrahim-oai]

This change is part of the following stack:

• Publish Python runtime wheels on release #21812
  • [1/8] Pin Python SDK runtime dependency #21891
    • [2/8] Generate Python SDK types from pinned runtime #21893
      • [3/8] Run Python SDK tests in CI #21895 ◀

_{Change managed by git-spice.}