ROTATE and MIRROR in the drawing plane moved a linear dimension's points
but left its stored rotation (the axis it measures along) unchanged. A
horizontal dimension rotated 90 degrees then measured its now-vertical
points along X and its value dropped to 0; mirroring about a slanted line
did the same. Polar ARRAY goes through the same path.
Turn the axis by the rotation angle, and reflect it about the mirror line.
A zero-length mirror line still leaves the dimension untouched.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>