Run Python unit tests in CI

[fabrizio2210]

Blocked by

Do not merge this pull request while #2752 is open.

This pull request is intentionally a draft. Once #2752 has an accepted and validated backward-compatible rollout approach, this branch should be updated to use it before being marked ready for review.

Summary

• restore the repository-wide test-python Makefile target from Run Slurm script unit tests in CI #2744
• restore the change-gated test-python GitHub Actions job
• include the job in the ci-success dependency set
• update two worker-test assertions to match the topology-plugin argument now passed on main

Why

This recreates #2744 after its revert in #2750 so Python unit tests can again run consistently in CI. The rollout must first address #2752: workflows triggered by pull_request_target need a backward-compatible way to run against existing pull-request heads and maintained release branches that may not contain newly introduced repository tooling.

The test runner discovers *_test.py and test_*.py files throughout the repository while pruning Git metadata, virtual environments, and Python cache directories. Each discovered test file runs in its own directory to preserve its local import behavior.

Validation

• env PYTHONDONTWRITEBYTECODE=1 make test-python: 108 tests passed (104 worker tests and 4 Slurm-script tests)
• parsed .github/workflows/one_job.yml with PyYAML
• git diff --check