`faulthandler` and `pv.OFF_SCREEN` as Defaults

[banesullivan]

Two module-level settings in PyVista's conftest are easy to forget but important:

1. faulthandler.enable() gives you a Python traceback on SIGSEGV/SIGBUS instead of a bare "Segmentation fault" message. This is the difference between a debuggable crash and an opaque one.

2. pv.OFF_SCREEN = True is required for headless test environments. Every PyVista downstream project sets this independently. Some forget and get hanging tests in CI.

Proposal

pytest-pyvista should set both automatically when loaded as a plugin:

import faulthandler
faulthandler.enable()

import pyvista as pv
pv.OFF_SCREEN = True

The OFF_SCREEN setting should be overridable via config for the rare case where someone wants on-screen tests:

[tool.pytest.ini_options]
pyvista_off_screen = false  # default: true

Related issues

• pyvista#7891 Segfault on self-hosted CI runners (closed, faulthandler was key to diagnosis)
• pyvista#1186 Disable the faulthandler warning (closed, discusses faulthandler noise in test output)
• pyvista#3746 _system_supports_plotting() unreliable (open, motivates OFF_SCREEN default)