- Restrict auth methods to PUBLICKEY only (no none, password, hostbased,
or keyboard-interactive advertised during negotiation)
- Log all denied channel types (session, x11, forwarded-tcpip) and
dangerous request types (exec, shell, subsystem, pty, env, x11, agent)
- Explicitly reject all dangerous channel request handlers (exec, shell,
subsystem, pty, env, x11, agent forwarding) with channel_failure
responses instead of russh's default silent Ok(()) which leaves clients
hanging and is a footgun if session channels are ever allowed
- Explicitly reject tcpip_forward, streamlocal_forward with logged warnings
- Log signal requests at debug level (harmless, no response needed)
- Override handlers in both core ServerHandler and NapiServerHandler
- Add tracing dependency to wraith-napi for security event logging
- Set preferred algorithms explicitly (russh::Preferred::DEFAULT which
uses only modern KEX/cipher/MAC algorithms)