script/install fetches the policy files from prompts over HTTP and
writes them into a repo, installing itself and script/update-policy
there. script/update-policy fetches the current script/install, runs
it on its own repo and commits without pushing. The file list and the
rules for keeping a repo's own entries move to script/install.
Model: opus-5-5
One command fetches the policy files a repo vendors from `prompts`, keeps the repo's own entries, commits them by name and pushes. A line the canonical file has never held stops the script before anything is written, as does a failed fetch. The canonical `.dockerignore` gains the closing comment the script needs. `test/update-policy.sh` runs in the `test` phase of `Dockerfile`.
Judgement call: `.gitea/workflows/check.yml` and `.prettierrc` are replaced whole.
Limitation: a repo with its own `.golangci.yml` settings, such as `sneak/homoicon`, stops until those are dealt with.
Model: opus-5-5