Review caught the explanation of the 0.015 round-trip break, not the
fix. Three copies of it claimed 16.015 rounds up while 16.005 rounds
down --- "opposite directions". Both round UP.
Verified rather than reasoned about: at the point the quantizer sees
them, 16.015 * 100 is exactly 1601.5 and 16.005 * 100 is exactly
1600.5. Both are exact ties, and half-up sends both away from zero.
So the mechanism is not opposed rounding, it is that half-up is not
symmetric under negation. Rounding up on the way in adds half a
centi-pixel; rounding up on the way out adds another, so the two
errors ACCUMULATE instead of cancelling, and 16.00 -> 16.02 -> 16.01
ends one centi-pixel high. "Opposite directions" would have predicted
them cancelling, which is the reverse of what happens.
Corrected in all three places that carried it: the module comment, the
test's doc comment, and framing section 3.2.
Comments only --- no behavior change, and the witness values in the
tests were already right. Zoom suite still 15/15.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016bqGA6s9tTUFzYpbeW3tai
Levi Neuwirth
1e054f7109