One session opens one or more PRs; one PR closes one or more tickets.
The implicit ticket-per-PR reading forced either an artificially wide
ticket or an artificially narrow PR whenever the natural unit of work
sat across a few tickets.
The floor and ceiling survive: no ticket, no branch, no PR; and every
PR closes at least one ticket or says why it closes none. The branch
name now carries the lead ticket only, which is exactly why the
closing keyword had to become mandatory in the same amendment.
law 9: the closing keyword is required, not assumed
Every PR merged on the forge up to today carried no closing keyword, so
tickets stayed open after their work landed on fastlane. Law 13 named the
PR body as the close mechanism; nothing made anyone write the line.
Law 9 now requires `Closes #n` per delivered ticket in the PR body, and
distinguishes it from `Refs #n`. The body is authoritative because it is
what survives a squash. The steward nudges on a missing keyword; it does
not close by inference and does not author PR bodies.
