COD-106 shared/collaborative remote tmux sessions (window-size latest + shared badge)

Two Codeman clients attaching the same durable remote tmux session at different
viewports would fight: tmux sizes a window to the SMALLEST attached client by
default. Push `window-size latest` to the remote session config so the window
tracks the most-recently-active client instead, letting concurrent clients
coexist; surface the client count for a "shared · N" badge.

Reconciled onto upstream PR #145: #145 moved the durable remote session onto the
dedicated `-L codeman-remote` socket under a `codeman-ssh-` name and scoped every
tmux set-option PER-SESSION (`set -t <name>`, never `-g`) so a shared remote tmux
server's OTHER sessions keep their own prefix/mouse/sizing. The original COD-106
commit added `set -g window-size latest` (GLOBAL) on the old `-L codeman` socket —
a regression against #145's hardening. This commit layers the window-size feature
onto #145's structure as `set -t <name> window-size latest` (per-session, on the
codeman-remote socket). Test assertions updated to the per-session form
(remote-shared-sessions.test.ts) and the byte-identical launch-command test
(remote-ssh-options.test.ts) extended with the window-size line — which supersedes
the separate f09323c9 assertion fix (dropped: it targeted the global form and also
carried unrelated CLAUDE.md doc changes).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/types/session.ts

@@ -127,8 +127,10 @@ export interface SessionRemote extends RemoteSshOptions {
 export interface RemoteSessionInfo {
   /** tmux session name (always starts `codeman-`). */
   name: string;
-  /** Whether a client is currently attached to the remote session. */
+  /** Whether at least one client is currently attached to the remote session. */
   attached: boolean;
+  /** COD-106 — number of clients attached (tmux `session_attached`); >1 = shared. */
+  attachedClients: number;
   /** tmux `session_created` epoch seconds. */
   created: number;
   /** Number of windows in the remote session. */