- src/session/tmux.ts: sync tmux CLI wrappers (available/has/kill), best-effort
- config: useTmux from USE_TMUX env (1/0/auto→detect tmux on PATH)
- session: when useTmux, spawn 'tmux new-session -A -s web_<id> <shell>' (the
node-pty proc is a tmux CLIENT); createSession takes an optional id for
re-attach; Session.tmuxName; kill() runs tmux kill-session
- manager: handleAttach re-attaches to a surviving 'web_<id>' tmux session after
a restart (Case 3.5); shutdown kills only the client pty for tmux sessions so
the shell keeps running
- tests: USE_TMUX:0 in shared integration cfg (no tmux leakage); unit CFGs
useTmux:false; integration 'H1' (real tmux): set var → restart server →
re-attach → var survived. 208 tests green.
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