buildMultiLineMappingResult booked Math.abs(roundingDiff) on the business
side regardless of sign, so a learned line_pattern whose ratios
over-allocate (three 0.3334 ratios on 100.00 kr = 100.02, diff -0.02)
produced an entry off by 2x|diff|. commit_journal_entry rejected it, so
the user saw a failed confirm and, since #1894, an unbalanced prefill.
The 3740 leg now lands on the business side for a positive diff
(under-allocation, unchanged) and on the opposite side for a negative diff
(over-allocation), flipped after the mirror. computeProposalLines gets the
identical rule in the same change to keep the byte-parity contract, and a
5000-amount sweep test pins engine and proposal together. Also reachable
with normalized ratios: 50/50 on 100.03 kr rounds to 50.02 + 50.02.
Closes#1898
Claude-Session: https://claude.ai/code/session_01FkUfWtuFCUkNtRAgMQCse2
Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Jakob Wennberg
175bb8bd92