A project saved before a printer or process option existed has no value
for it. The GUI takes such keys from the project's system preset; the
CLI left them at the option default, so e.g. extruder_clearance_dist_to_rod
sliced as 40 instead of the P1S's 33.
The CLI now resolves the project's system printer and process presets by
name and copies the keys the project lacks, skipping preset bookkeeping,
print-host keys, the extruder variant layout and keys the legacy handler
drops. PresetBundle::resolve_system_preset finds the vendor through its
manifest or preset cache, so it also works in release builds, which ship
vendors as caches only.
