feat: tmux-agents v1.18.0 tracks replies and makes attention explicit
I shipped v1.18.0 of tmux-agents, which tracks completion per request: each tmux-ask request resolves when its own reply arrives, whoever asked, so answering an agent other than its parent no longer leaves the receiver working or falsely showing "needs you". A delivered request with no observable progress for 30 minutes now shows "reply overdue" on the receiver, with a configurable timeout separate from "needs you". When an agent in a tmux-spawn --split pane exits, the pane returns to the default shell with its original environment; @tmux_agents_sub_exit keep preserves the old dead-pane behaviour. Any tracked agent, including a top-level main, can now use tmux-agent-report --needs-you "reason" to ask for me explicitly, with the reason shown in the chip and agent list.