The same DXF/DWG bulge → (center, radius, sweep) formula was inlined
in six places (hatch outline, polyline tess + truck path, lwpolyline
×4, scene hatch fill, explode bulge_to_arc) — each with subtly
different sweep-direction handling for the bulge sign.
Add `entities::common::BulgeArc { center, radius, start_angle,
end_angle, sweep }` with one `from_bulge(p0, p1, bulge)` constructor
and a `sample(t)` helper. Callsites collapse to a few lines.
Net: -121 lines, one canonical sweep-direction convention shared by
all consumers.
array.rs (the path-along-curve f32 helper) keeps its inline math —
its sign convention is inverted relative to the others and changing
it without exercising the array-path command risks regressing the
output.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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