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/wiki/Core-Concepts.md

@@ -97,7 +97,10 @@ would. That indirection buys:
 - **Real scrollback.** History is held by tmux, so reconnecting replays what happened while
   you were gone instead of starting from blank.
 - **Attach from anywhere else.** The same session is reachable from a terminal over SSH
-  with `codeman tui`, or plain `tmux -L codeman attach`.
+  with `codeman tui` (F1 detaches), `./scripts/tmux-manager.sh` (likewise F1), or plain
+  `tmux -L codeman attach`. A plain attach has no detach key: Codeman keeps tmux's prefix
+  table on its socket down to `send-prefix`, so `Ctrl+B d` does nothing there; leave it
+  with `tmux -L codeman detach-client` from another shell, or bind a key yourself.
 - **Secrets off the command line.** Environment overrides are injected with socket-scoped
   `tmux setenv` rather than being visible in the spawn command.