chore: record the settled planning questions of the headless coordination intent

[REPPL]

The intent for several headless agents working one repository through the shared remote is still a draft, and is not planned here: the product thinker is away, and three of its questions are genuine product trade-offs they answer first. This change records, as facilitator decisions on delegation, the questions its own record or the state of the art already settles, so that planning starts from them.

The decisions:

• The coordination pass: it runs on demand before land, build, drain and status act, with no timer and no long-lived process.
• Dependencies and rebuilds: a dependency is a Depends-On: line in the pull request's body, and a waiting branch is rebuilt by merging the default branch in, never restacked. A dependency holds back only the landing; the waiting branch's own work goes on.
• Budgets: the machine budget is the load gate's existing slots, weighted per job. The model budget stays a fixed count per run.
• Credentials: an autonomous session's credential is a token the repository's GitHub App mints. Registering the App is one browser step the person takes. The session acts under the person's name, through the App.
• Holds and release cuts: a hold is a reservation, and the release cut's hold is the announcements' reservation.
• Generation number: the claim's tip commit serves as the generation number.
• The central view: it is abcd status, one fixed-form line per working copy with its own expiry, carrying the session's state (working, waiting or stopped) from the checklist intent.
• The criteria made testable: the push-rate bound, the version refusal, branch deletion and the mechanism's baseline. A waiting session wakes before half its lease, and the coordination principle has a stated bound.
• Ordering: the overnight-stall fix ships first, ahead of this intent.

Refs: itd-2610170634394993, itd-2610170638184486
Refs: iss-2610170619247185

Assisted-by: Claude:claude-opus-5-5