Dara ruled the C Garage window open from the garage floor (2026-09-19,
again 2026-10-04). Riot's lines close it for layer 0, so the builder now
takes them off there (`cleared` in haven.edits.json) and the test is back.
Short stretches with no line alongside borrow every line tied for nearest,
so the result no longer depends on list order. Visible-floor leaks
2,327,130 -> 2,323,163, false shadow 33,824,793 -> 33,816,275.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>