Slate v2 Roadmap Closeout

Supporting plan. For current queue and roadmap truth, see master-roadmap.md.

Goal

Mark the roadmap/doc stack as coherent enough that further default roadmap grooming is no longer the main queue.

Result

• the Phase 10 release-readiness stack is now coherent:
  • package truth
  • root/public truth
  • stop/go decision
  • blocker checklist
• further roadmap work should be selective only when:
  • a new family row materially changes the replacement decision
  • or a real package/API seam changes
• otherwise the next work should be implementation or shipping work, not more roadmap churn