Chord error 2.5 -> 10 cm, shell work skipped outside the 0-0.75 m band. Sweep pairs -39%, prepare -60%,
near-ready 3-8% faster than L115 but still +13..+22% vs L109. Floor offset 7.88 mm; captures match L115
by eye; fast tier, walk audits, Clang/GCC W1/W8/W12 determinism green. Not for merge yet.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1