Three coupled changes to /implement:
- Boss-context offload via single subagent dispatch (target ~100x reduction)
- Iter isolation via branches (eliminates parallel-implementer conflicts)
- Per-iter journals under docs/journals/ replacing the JOURNAL.md monolith
JOURNAL.md becomes docs/journal-archive.md at acceptance time. Workers
stay at Opus 4.7; saving comes from token-volume relocation only.
