v0.0.3

Other

• gate mask_mode to cfg(unix) and fix 4 broken rustdoc intra-doc links
• Merge client + FFI + agent + zeroize security fixes
• Merge server + sshd security fixes
• Merge auth/hostkey/key/known_hosts security fixes
• Merge transport/KEX/compression security fixes
• gate loopback SFTP roundtrip test to cfg(unix)
• round-2 fixes — macOS SUN_LEN, Windows clippy, aarch64 cross binary

Security

• (agent) replace libc unsafe with nix + MetadataExt in SSH_AUTH_SOCK validation
• (sftp) gate jail-prefix hiding in op_realpath behind opt-in
• rustfmt cleanup across channel/scp/sftp test+impl
• (forwarding) X11 single_connection, tcpip-forward allow filter, X11 cookie note
• (scp) O_NOFOLLOW recv, canonicalised base, reject '.' name
• (sftp) jail-aware symlink rejection, set_len cap, mode masking
• (channel) reject traffic on unconfirmed channels