kunchenguid/firstmate ? reverse-engineered prompt

Build me a repo I can open in a supported coding agent on macOS or Linux that turns that one agent into a kind of first mate for a whole crew. I should only have to chat with the main agent, then it should spin up separate workers for different jobs in parallel, like fixing bugs, planning work, auditing something, or adding a feature. Each worker should run in its own visible terminal session and use an isolated git worktree so tasks do not step on each other.

I want it to be a portable folder of instructions, skills, helper scripts, and state, not a big separate app. It should supervise the crew, keep progress on disk so it can recover after a restart, and bring back clear outcomes like a PR ready to review, an approved local merge, or a written investigation report. Please include safe project modes, guarded behavior around repo changes, and support for Claude Code, Grok, Pi, Codex, and OpenCode. Look up current docs online if you need to.