OptionaldecimationOptionaltargetTarget segments per chunk before closing at the next layer boundary (default 250_000).
OptionaltubeTube-mode memory budget (RR-006): when set, 'auto' decimation is additionally raised so the kept
extrusion-segment count stays ≤ this budget — tube geometry is ~23× the memory of lines, so a
segment count that is harmless as lines OOMs as tubes. Ignored when an explicit numeric decimation
is given (a caller override wins). Omit for lines mode → behavior unchanged. Disclosed via
ChunkBuildResult.decimationApplied like any decimation.
Decimation factor N (keep every Nth extrusion segment) or 'auto' (§4.4 thresholds).