The previous walk-back in SetCalibrationEntry was unconditional, corrupting
short valid units ending in multi-byte characters (e.g. Omega, mu, degree).
Also failed to drop an orphaned lead byte left after stripping continuation
bytes. Restructured to use a 256-byte staging buffer so truncation can be
detected, then repair runs only in the truncation branch. Algorithm now
matches Go CalConfig.Normalise() exactly: scan back over continuation bytes
(up to 3), find the lead byte, derive expected sequence length, cut if
incomplete. Covers all cases: orphaned continuation, orphaned lead, cut on
lead byte.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
