Supersedes 71221837. Samples every t* 0.5 (interval-mean forces), trailing
t* 50..60 window (21 samples); range <= 10 % and |slope*window| <= 2 % of
each official band width. Verdict on the window mean with the distance to
the nearest band edge. Our engineering rule, frozen before any run.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
(cherry picked from commit 869d60d78e)