Set up a dev-local launcher for this codebase

Goal: produce one script (scripts/dev-local.sh) that a person or agent runs to bring the whole local stack up — every long-lived dev server in its own tmux window, plus any infra (DB, cache, queues) the app needs — and a short skill doc so it's discoverable later.

Do NOT start any dev servers yourself. You are generating the launcher, not running it. Build it, syntax-check it, then hand it to the user to run.

This is the local, single-stack launcher. For concurrent agents that each need their own isolated stack (one laptop can't run N), see crabbox-setup — the cloud counterpart. It reuses this script's service/port discovery, so set this up first.

Step 1 — Investigate the repo (don't guess)

Discover the real facts before writing anything: