feature: tmux-agents v1.0.0

I shipped v1.0.0 of tmux-agents, extracted from my dotfiles with its full history and released under MIT, because I want my sub agents' work to stay visible after the task ends. Each Claude or Codex sub agent runs in its own tmux window: I can watch a live preview, switch in to steer it, and let agents exchange tasks and replies through tmux-ask. The panes stay until closed, the conversations can be resumed afterward, and a line above the status bar flags agents that need me. There's also a setup skill so an agent can install it and walk me through a quick start.