fix(tmux): keep browser keys from switching a tab onto another session (#669)

Squash of PR #669. Browser terminals could be moved onto another session
by tmux's prefix keys: Ctrl+B then ), (, s or w switched the tab's tmux
client to a different session while the tab kept the original's name.
Codeman's tmux socket now keeps only Ctrl+B Ctrl+B (send-prefix) in its
prefix table, and codeman tui and scripts/tmux-manager.sh get F1 as their
way out instead of Ctrl+B d.

Merge-time fixes by the maintainer: on an empty prefix table the
unbind-key that fails no longer skips binding send-prefix; a key tmux lists
escaped (prefix C-\ shows as C-\\) compares equal, so the reset does not rerun on every create;
and reconcileSessions() reduces the table at boot when the socket has live
sessions, so sessions that survive an upgrade are covered too.

Co-authored-by: christianhaberl <116439789+christianhaberl@users.noreply.github.com>
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/tui.md

@@ -178,8 +178,11 @@ bar first named the wrong letter (tmux binds lowercase `d` to `detach-client` an
 capital `D` to `choose-client`), and once corrected it still failed for anyone who
 kept Ctrl held, because that sends `Ctrl+D`, which tmux leaves unbound. So the TUI
 claims `F1` in tmux's prefix-less key table for the length of the attach and gives
-it back afterwards. The chord still works; it is simply not what you are told to
-press.
+it back afterwards. The held-Ctrl chord (`Ctrl+B Ctrl+D`) works too, as the TUI
+claims it for the attach as well. Plain `Ctrl+B d` does not: on Codeman's socket
+the prefix table holds nothing but `send-prefix`, because the browser's terminals
+are tmux clients on the same server and must not be able to `switch-client` or
+`detach-client` themselves (`src/tmux-prefix-table.ts`).
 
 You do not have to remember any of it. For as long as the attach lasts the pane
 wears a bar across the top: