New pass 8 (core/domain/diff_check.{hpp,cpp}): every complete local diff
pair (X_P/X_N, name-based) resolves its legs to two bridged nets; peer
pairs on those nets must match leg for leg.
- DiffPolaritySwap: P legs meet N legs across a connection (sometimes
intentional - reported for review), or both legs joined onto one net.
- DiffCrossIncomplete: pairs sharing only one leg, and diff-bus lanes
crossing NOWHERE while sibling lanes cross (distributed/fan-out buses
stay silent - validated against the real 7-card VPX system: 21 noisy
findings down to 3 genuine dangling-lane reports, 0 false swaps).
diff_suffix/split_trailing_index/is_internal_name promoted out of
analysis.cpp's anonymous namespace for reuse. VerifyReport.diff_anomalies
wired into model_total() and all four renderers (TUI verify, script
engine, wx log, analyze Issues). 8 new test cases (466 assertions).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
