terminal: stop replaying questions, stop opening two sockets, bind the word keys

three separate faults behind "reconnecting gets weird and the keyboard is not
natural".

── the replay typed into the shell ──

the pty buffer was stored raw and replayed verbatim on every re-attach. anything
in it that ASKS the terminal a question — DSR, DA, DECRQM, XTVERSION, XTGETTCAP,
the OSC colour queries — got asked again, and xterm answered correctly by writing
the reply to its input. the pty receives that as a keystroke nobody typed.

stripped on the way IN, since the buffer is the thing that gets replayed and a
live client already answered them once when they were legitimately asked. only
questions are removed; everything that draws is untouched. where a control shares
its final byte with one that draws, the parameter is enumerated rather than
wildcarded — CSI 18 t asks the window size, CSI 22 t pushes the title, and
stripping the second would change what a replay renders. 36 tests, both
directions, because both fail silently.

── two sockets on one session ──

handleClose armed a reconnect timer; handleVisibilityChange fired on tab focus
whenever readyState was CLOSED — which is exactly what a pending timer leaves.
both ran. every keystroke went twice, two replay frames fought over the screen,
and only one socket was ever cleaned up because __terminalCleanup is overwritten
by whichever connect ran last. connect() is now the single guard, and a stale
socket's close no longer speaks for the session.

── the keyboard ──

alt-arrow was dead for everyone: xterm.js 5 rewrote it into the ctrl-arrow
sequence, xterm.js 6 removed that rewrite and emits the honest ^[[1;3C/D
(verified — the string 1;3D does not appear anywhere in the 6.0 bundle). nothing
bound it. so it broke on a dependency bump, with no shell config changed.

bound in zsh rather than translated in the browser, deliberately: tmux.conf
claims M-Left/M-Right for pane switching, and a client-side rewrite would send
^[b to tmux and break it. the real sequence lets tmux handle it inside a session
and zsh outside.

ctrl-arrow was worse and more embarrassing: it worked for MEMBERS and not for the
OWNER. shell-skel/zshrc has had the bindings all along; the owner's .zshrc is
assembled in machine-setup and never got them. the owner had a strictly worse
shell than the accounts they provision. confirmed with `zsh -i -c bindkey`
before and after.

also: escape-time 10 in tmux.conf. the 500ms default delays every Alt chord and
every Escape, which is most of what "not natural" felt like.

applied to this host by hand — setup only runs at install. cmd+arrow is left
alone: xterm emits nothing for it, so there is no sequence to bind.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

scripts/setup/tmux.conf

@@ -24,6 +24,12 @@ bind - split-window -v
 unbind r
 bind r source-file ~/.tmux.conf \; display-message "Config reloaded!" \; refresh-client -S
 
+# Meta keys are ESC-prefixed on the wire, and tmux waits `escape-time` to decide whether an incoming ESC is
+# a lone Escape or the start of one. The default is 500ms, so every Alt-chord below — and every Escape in
+# vim — pays half a second before anything happens. 10ms is enough to disambiguate a sequence that arrives
+# in one TCP frame, which over a websocket relay it always does.
+set -sg escape-time 10
+
 # switch panes using Alt-arrow without prefix
 bind -n M-Left select-pane -L
 bind -n M-Right select-pane -R