Move client_t I/O and lifecycle out of ssh_server.c into a dedicated
module. ssh_server.c is now down to the listening socket, host key
setup, ssh_server_init / ssh_server_start, and the accept loop.
Migrated to client.{c,h}:
- client_send, client_printf
- client_addref, client_release (and the ssh_session / ssh_channel /
channel_cb teardown that fires on the final release)
- client_install_channel_callbacks
- client_channel_window_change / _eof / _close (the post-bootstrap
callbacks that target the client_t)
The client_t struct definition stays in ssh_server.h so we don't have
to revisit every existing #include chain. bootstrap, commands, exec,
input, and tui pick up the new client.h alongside their existing
ssh_server.h include.
ssh_server.c shrinks from 402 to 249 lines (-153).
Final per-module size after PR2:
ssh_server.c 249 accept loop + ssh_server_init/start + host key
bootstrap.c 493 per-connection SSH handshake / auth / channel
client.c 162 client_t I/O + lifecycle + channel callbacks
input.c 637 username read + handle_key + main loop +
notify_mentions + idle timeout
commands.c 269 vim ':' command dispatcher
exec.c 453 SSH exec subcommand dispatcher
ratelimit.c 197 IP rate limit + connection counters
tui.c 614 screen rendering
chat_room.c 151 room + client list
message.c 350 message log load/save/search
utf8.c 250 UTF-8 width / validation
common.c 133 buffer_*, env_int, is_valid_username,
sanitize_terminal_size, tnt_state_*
main.c 109 process entry
Total: ~4 000 lines of C across 13 files, no file over 650 lines, every
file is single-purpose. Behaviour is preserved: the migrated code is
byte-for-byte identical.
