"""Integration tests: real widgets, real services, no network (R10-T01 layout).

These build actual Qt widgets offscreen (``QT_QPA_PLATFORM=offscreen``) and run
a turn end to end with a scripted :class:`FakeProvider`. They are slower than
the unit suite - a QApplication has to exist - and are what proves the seams
introduced by R03/R04 are actually wired into the screens, not just correct in
isolation.
"""