The per-vertex `bulges` list was handed out in the entity's own frame next
to `points` that had been translated to WCS. A mirrored LWPOLYLINE
(extrusion / Normal -Z, what `entity_mirror` produces) is a reflection,
which reverses every arc's sense, so the reader tested endpoints against
the arc's mirror image: a line ending on the true apex dangled, a line
ending on empty paper made a junction, and `length` (frame-invariant)
said nothing. Both engines had it — ezdxf emitted `get_points("xyb")`
raw, COM returned `GetBulge` raw after reflecting `Coordinates`.
`ocs.wcs_bulge(extrusion, bulge)` now negates the sign for a left-handed
frame (the same rule `wcs_arc_angles` applies to an ARC's endpoints) and
both `_entity_info` paths route bulges through it whenever they translate
the points. Fenced by an end-to-end mirrored-pipe graph test, the COM
`_entity_info` fake with Normal -Z, and a boundary-level OCS test.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
