feature: Support Tmux control mode

[jpmcb]

When using Tmux's "Control Mode":

# start in control mode and ignore control mode system echos
tmux -CC

Ghostty indefinitely hangs with the cursor just blinking. This is more or less expected since Ghostty doesn't seem to have integrated with Tmux in this way (MacOS's default terminal does the same thing).

Control mode is a textual protocol for Tmux to interface with applications and allow for applications to control Tmux. iTerm uses it to dynamically incorporate its native tabs and panes as Tmux windows and panes respectively. So, in iTerm with Control Mode, when creating a new window with ctrl-b c, a native iTerm tab is created.

You can get an idea from how this works by inspecting the output with just 1 -C:

❯ tmux -C
1000p%begin 1732716043 76540 0
%end 1732716043 76540 0
%window-add @4
%sessions-changed
%session-changed $4 4
%window-renamed @4 tmux
%output %7 \033[0m\033[49m\033[39m\033[27m\033[24m\015\033[K\015\012\015\012\033[2A\0337\033[0m\033[49m\033[39m\033[0m\033[49m\033[38;2;87;199;255m~\033[0m\033[38;2;87;199;255m\033[49m\033[38;2;87;199;255m\033[0m\033[38;2;87;199;255m\033[49m\033[30m\033[0m\033[38;2;0;0;0m\033[49m\033[39m                                                                      \033[0m\033[49m\033[38;5;242m07:00:43\033[0m\033[38;5;242m\033[49m\033[38;5;242m\033[0m\033[38;5;242m\033[49m\033[38;5;242m\033[0m\033[38;5;242m\033[49m\033[39m\015\012\033[0m\033[49m\033[38;2;255;106;193m❯\033[0m\033[38;2;255;106;193m\033[49m\033[38;2;255;106;193m\033[0m\033[38;2;255;106;193m\033[49m\033[30m\033[0m\033[38;2;0;0;0m\033[49m\033[39m \033[0m\033[49m\033[39m\033[?2004h
%output %7 \033[?25l
%window-renamed @4 zsh

# etc. etc. etc.

From the Tmux man page:

CONTROL MODE
     tmux offers a textual interface called
     control mode.  This allows applications to
     communicate with tmux using a simple text-
     only protocol.

     In control mode, a client sends tmux commands
     or command sequences terminated by newlines
     on standard input.  Each command will produce
     one block of output on standard output.  An
     output block consists of a %begin line
     followed by the output (which may be empty).
     The output block ends with a %end or %error.
     %begin and matching %end or %error have three
     arguments: an integer time (as seconds from
     epoch), command number and flags (currently
     not used).  For example:

           %begin 1363006971 2 1
           0: ksh* (1 panes) [80x24] [layout b25f,80x24,0,0,2] @2 (active)
           %end 1363006971 2 1

[mitchellh]

Dupe #1935

[jpmcb]

Whoops! Thanks Mitchell!