Add tcp_timestamps, tcp_window_scaling, tcp_sack, tcp_ecn, ip_no_pmtu_disc,
and tcp_fin_timeout to every OS profile in OS_SYSCTLS.
All 6 are network-namespace-scoped and safe to set per-container without
--privileged. They directly influence nmap's OPS, WIN, ECN, and T2-T6
probe groups, making OS family detection significantly more convincing.
Key changes:
- tcp_timestamps=0 for windows/embedded/cisco (strongest Windows discriminator)
- tcp_ecn=2 for linux (ECN offer), 0 for all others
- tcp_sack=0 / tcp_window_scaling=0 for embedded/cisco
- ip_no_pmtu_disc=1 for embedded/cisco (DF bit ICMP behaviour)
- Expose _REQUIRED_SYSCTLS frozenset for completeness assertions
Tests: 88 new test cases across all OS families and composer integration.
Total suite: 812 passed.