Catches the iXex/IDEX parallel-printing branch up to upstream main
(102 commits). Two content conflicts resolved:
- src/libslic3r/Preset.cpp: s_Preset_printer_options — kept upstream's
new "use_3mf" key and our iMEX printer-capability/mode keys.
- tests/fff_print/test_gcodewriter.cpp: upstream revived the disabled
suite (#14196), dropping the obsolete [.]-tagged lift() test and its
config_lift_unlift.ini; kept their set_speed + z_hop tests and appended
our 10 per-firmware set_pressure_advance/set_temperature scenarios.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>