fix(tmux): stop nested prefix keys and TUI Alt+digits from moving other clients

Docker and owned-remote tmux servers kept the stock prefix table, so Ctrl+Q
then )/(/s/w/L switch-client'd the inner client onto a sibling. Those create
chains now leave only C-q send-prefix.

codeman tui bound M-1..M-9 in the server-wide root table. The keys stay, but
switch-client runs only for the attaching client (tty plus a one-shot pid).
A browser tab's Esc-then-digit no longer jumps sessions, and a killed TUI
leaves a binding that matches no live client.

Co-authored-by: DDT <1786035110@qq.com>

test/remote-ssh-options.test.ts

@@ -164,6 +164,12 @@ describe('COD-107 buildRemoteLaunchCommand — threads connection args', () => {
       'set -s escape-time 0',
       // COD-106 — shared/collaborative sizing, per-session scoped (never -g).
       `set -t ${remoteName} window-size latest`,
+      // #671 — the nested server's prefix table is stock unless this chain
+      // reduces it. Ctrl+Q then ) would switch-client onto a sibling session.
+      // Before remain-on-exit: a remote tmux that rejects `failed` aborts the
+      // rest of the chain, and that option has to stay last.
+      'unbind-key -a -T prefix',
+      'bind-key -T prefix C-q send-prefix',
       // #210 — keep a CRASHED pane for diagnosis. `failed` (not `on`, which would
       // also strand a pane after a clean `exit`), and LAST because tmux aborts the
       // remaining commands of a `\;` chain on error and `failed` needs tmux >= 3.2.