Connect() reports a password-required marker instead of a raw handshake
error when a regular SSH server turns down the NetBird key, so the caller
can prompt and retry as often as the user needs. NetBird servers are
excluded: they authenticate with a JWT or the NetBird key, so a failure
there is genuine. The marker is a string because gomobile flattens errors
to their message across the binding.
Errors that reach the terminal are unwrapped to their root cause, so a
dial failure reads "i/o timeout" rather than repeating every layer that
added context; the full chain still goes to the log. A normal shell exit
no longer surfaces as "EOF".
Reset() lets a closed client back a reconnect, which keeps the Java-side
session and its scrollback alive across a drop, and the JWT flow now
reports that it is waiting on the browser instead of blocking silently.
Exposes SSHClient + SSHTerminalListener to the Android app. Connect()
auto-detects the server type via banner inspection and selects the auth
path: NetBird-SSH with JWT triggers the device-code OAuth flow via the
existing URLOpener; NetBird-SSH without JWT uses the NetBird private
key; regular SSH falls back to NetBird key then optional password. The
client dials through the running tunnel using a plain net.Dialer and
relies on the gomobile-bound listener for streaming PTY output back to
Java for rendering in an xterm.js WebView.
