A tab trims the perimeter short of its entry, but the lead-out was still
generated from the nominal entry point. An arc lead-out therefore started
off its own radius (ExecutionMotionReader rejected it as inconsistent), and
a line lead-out ran diagonally back toward the entry.
Every lead-out style on a tabbed perimeter now leaves from the trimmed
cut's actual end, on that entity's normal, so arcs are tangent and the tab
gap stays uncut. Untabbed contours and the corner run-out rules are
unchanged. Malformed legacy output is still refused, never refit.
Red before the fix: the three tabbed arc cases threw "Arc has zero or
inconsistent radius" and the line case ended at y=5 instead of 4.8. Keeping
the entry's normal at the actual end fails the curved-perimeter case.
aj