feat(claude): search for an existing tool before writing one

[thompsonson]

Twice now a script has been written and thrown away because an equivalent already existed. This adds the rule that would have caught both.

Today's instance

I wrote a GitHub Actions runner setup script for thompsonson/atomicguard, staged it on computer, and had it reviewed twice. setup-gha-runner.sh was already sitting in ~mt on that same machine, and on main in thompsonson/dev at scripts/gha-runner/.

The existing one was better in ways that mattered:

• It runs bin/installdependencies.sh. Mine skipped it, so my runner would most likely have failed to start.
• It waits for Listening for Jobs in the journal. Mine gated on systemctl is-active, which is true for a service that is up but not talking to GitHub.
• It preflights isolation, including that sudo -u gha-runner ls /home/mt fails. That machine holds GPG secret keys.

Why the searches missed it

I looked in dotfiles and in the host's PATH. Neither covers a script in a user's home directory, or one in a sibling repository. gh search code --owner thompsonson found it in one call.

The rule

## Before you build

- Search for an existing script or tool before writing a new one.
- Look in the repository, in my other repositories, and in the home directory of the machine that will run it.
- `gh search code --owner thompsonson "<distinctive string>"` finds it when a local search does not.
- Improve what exists rather than writing a second one beside it.
- Say what you searched, so I can point you at what you missed.

The last bullet is the cheap one: saying where I looked lets you correct a wrong guess before the work is done, rather than after.

./tests/test.sh quick passes, 7/7.

https://claude.ai/code/session_01VUd2Wv3nkSBpWgYBK6yhfh