Reclassify every rsync-compatibility row as parity / caveat / divergent
(replacing the misleading 143-OK / 0-divergence summary), and document the
protocol 2.23.0 behavior:
- Split the conflated `-M, --preserve` row: `-M` is `--remote-option`,
`--preserve` is the FastSync `-p`+`-t` alias.
- Fix `MAX_CONNECTION_MEMORY` (256 MiB, not 1 GB), `--rsync-path`
(client-only, never crosses the wire), and the `-p` mode behavior
(strict rsync parity; no masking).
- `--specials` now recreates sockets, so `-D` is real parity; fake-super
records the resolved owner and replays mode/time (never real-chowns).
- Document short options/clustering, checksum/compression choices, seed
randomization, timeout/max-alloc defaults, temp-dir confinement + EXDEV,
identity/map parity, verbatim symlinks, delete scoping, `--max-delete`
partial + exit 25, `--chmod`, output caveats, and server `--port`.
- Bump version refs to 2.23.0 and add the 2.23.0 CHANGELOG entry.
Docs-only; no source changes.
Add POSIX ACL/xattr tooling (acl, attr), zstd/lz4/xxhash dev libs and build rsync 3.4.1 from source so drop-in parity tests can run inside CI. Bump all workflow/agent image references v10 -> v11.
Split FastSync's single use_metadata bundle into four independent rsync-parity attributes: preserve_perms, preserve_times, preserve_owner, preserve_group. use_metadata is now a derived transport bit (config_derived_use_metadata).
CLI: real -p/--perms, -t/--times, -o/--owner, -g/--group plus --no-perms/--no-times/--no-owner/--no-group (short and long) and --no-preserve; -a is now rsync -rlptgoD; --preserve = -pt; -A implies -p; -X does not; --chmod implies -p; --usermap/--groupmap/--chown imply owner/group per side; --incremental/--delta still auto-preserve unless negated.
Receiver: per-attribute FileAttrPolicy gating for files, dirs (modes applied at end of transfer), symlinks and specials; rsync -E read-bit rule; new files get source_mode & ~umask sanitized (no group/other write); per-side identity resolution; deferred directory metadata; batch dir-metadata replay; daemon modules without 'client owner = yes' no longer refuse plain -a but force super off (no ownership) with a warning.
Wire: PROTOCOL_VERSION 2.21.0 -> 2.22.0 (four appended config bools, golden 653 / 95530566005420798). FileMetadata/chunk/batch framing unchanged. Docs/CHANGELOG/CMake updated to 2.22.0.
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