Resolved 4 conflicts:
- PrintConfig.hpp / Preset.cpp: upstream restored calib_flowrate_topinfill_special_order
(removed in the prior merge, now re-added and re-registered); kept it alongside our
IMEX options (imex_parallel_mode, imex_head_filament_map).
- Plater.cpp: kept our <sstream> include plus upstream's <optional> and plugin includes.
- tests/fff_print/test_gcodewriter.cpp: both sides appended disjoint scenarios after a
shared base. Reconstructed as upstream's full file (base + its 3 toolchange/H2C
scenarios + the boost/filesystem include its helper needs) followed by our 10
set_pressure_advance / set_temperature scenarios. 22 scenarios total, no duplicates.