Enforce one-task, one-branch, one-worktree, one-agent, and stop scaling past 5–7.

The binding rule for parallel coding agents, deviate and race conditions come back. Budget ~5 GB disk per worktree (six agents burned 9.82 GB in 20 minutes), and throughput degrades past 5–7 agents from rate limits and the human cost of reviewing six PRs at once. Gate each task on file exclusivity, interface stability, and single-sentence scope.