Commissioned by Jason 2026-08-13: agents need the branch-handling
process written down — next-first for every contribution, Jason-only
promotion merges to main, the gate sequence (issue, next-head base,
terminal-green CI on the exact head, independent review, no self-merge,
pinned-head merge), role responsibilities, and the hotfix/divergence
rules motivated by the #1152 main-only landing.