test(parity): option-wave rsync differentials + docs (109/21/26)
- tests/integration/test_option_parity.py: bwlimit parse matrix + throttle
rate, --info flist/name/nonreg/del(dry+real+itemize)/remove, real-setpriv
--ignore-errors, rsync-daemon -M forwarding evidence, filter protect/risk
destination-only divergence pin.
- RSYNC_COMPAT.md: tally 109/21/26; --bwlimit and --ignore-errors -> Parity,
--filter and -M -> Divergent with differential rationale, --info residual
narrowed to the categories with no client-observable event.
- HANDOFF/README: protocol 2.27.0, option-wave summary.