Development record

The enqueue step at .abcd/development/brief/04-surfaces/38-land.md:106 says the pull request is armed where the merge gate allows it and names no other hold. internal/core/landing/stacked.go also defers the arming where a merge queue gates the default branch and the branch shares a commit not on it with another queued or armed pull request, and the step then stops naming it. `abcd land --help` documents this; the chapter does not.