docs: record pull request 4 as the subject to land

[juliantellez]

What. Records the pull request to land next, in docs/subject.md. It is pull request 4,
#4. No code changes.

Why. The next step runs in a new session and reads nothing from this one. The file names the
number, the title, the head branch, the head commit, the conflict state and every check that is not
passing.

Pull request 4 is the oldest of the five open pull requests and the only one carrying a failing
check. That check is plan and apply. gh pr checks 4 does not show it, because the deploy
workflow does not start on a pull request, so read the check runs on the commit instead.

No check is required in this repository. main is not protected and the ruleset list is empty. The
file states that judgement rather than hiding it.

Pull requests 5, 6 and 7 each add a file called subject.md at the root. The first to merge makes
the other two conflict on add over add. This pull request writes to docs/subject.md so it does not
join that pile.

Gates run locally on this branch: typecheck, lint, 75 of 75 tests, build, the package start, and
terraform fmt plus validate. All pass.