The test forces GraphicsBackend=opengl and builds a full MainWindow
with QOpenGLWidget-based viewer panels. On headless platforms whose
QPA cannot provide a GL context (Ubuntu/Windows CI on offscreen), the
app's GL calls crash on a non-current context (SEGFAULT in CI on
both). Probe with QOpenGLContext+QOffscreenSurface and GTEST_SKIP when
GL is unusable; the test still runs on platforms with real GL.
Mike-Solar
9ca2b0e716
