Skip Qt workflow tests when PySide6 is not installed in core CI

[Copilot]

The test (ubuntu, py3.11) workflow was failing during pytest collection because tests/test_workflow_process.py imported PySide6 unconditionally, while the core test job does not install the desktop Qt dependency. This change scopes the Qt dependency to the tests that actually need it so the rest of the workflow-process coverage still runs in headless CI.

• Root cause

  • tests/test_workflow_process.py imported QProcess and ProcessWorkflowWorker at module load time.
  • In the core Ubuntu test job, PySide6 is absent by design, so collection aborted before any tests in the module could run.

• Change

  • Replace the module-level Qt imports with a small helper that resolves Qt-only dependencies lazily.
  • Use pytest.importorskip("PySide6") inside that helper so GUI-specific tests skip cleanly when the desktop extra is not installed.

• Effect

  • Non-GUI workflow tests in test_workflow_process.py continue to execute in the core CI environment.
  • Only the ProcessWorkflowWorker tests become conditional on PySide6, matching the package's optional dependency model.

def _process_worker_dependencies():
    pytest.importorskip("PySide6")

    from PySide6.QtCore import QProcess
    from PyHydroGeophysX.qt_apps.workers import ProcessWorkflowWorker

    return ProcessWorkflowWorker, QProcess