Refactor base_tr fixture to remove SlurmSystem dependency

[coderabbitai]

Background

In PR #779, during review of the Kubernetes test sanitization, it was identified that the base_tr fixture unnecessarily depends on SlurmSystem, which causes Kubernetes-only tests to instantiate both a KubernetesSystem and a SlurmSystem.

Proposed Change

Update the base_tr fixture definition in tests/conftest.py:

Current:

def base_tr(slurm_system: SlurmSystem) -> TestRun:

Proposed:

def base_tr(tmp_path: Path) -> TestRun:

This change will make the fixture system-agnostic and avoid unnecessary system instantiation in tests that don't require SLURM.

Tasks

• Update base_tr fixture signature to use tmp_path: Path instead of slurm_system: SlurmSystem
• Fix all usages of base_tr throughout the test suite to work with the new signature
• Verify all tests still pass after the refactoring

References

• Original discussion: Address issues with Sleep test over K8s #779 (comment)
• Related PR: Address issues with Sleep test over K8s #779

Requested by: @amaslenn