Schema-declared achieved status for open-world rollups

The deferred "option B" from the WORK-296 achievement-status discussion. Today plan-progress computes its achieved subset with a hardcoded union of terminal statuses (value="status:/^(done|fixed|accepted|complete)$/", decision C). That is correct and minimal, but it bakes domain knowledge into the plan sugar and relies on achieved-status name uniqueness across types — which holds for the five first-party plan types but is not guaranteed for a third-party "trackable" type that introduces its own status lifecycle.

This item makes achievement self-declared on each rune's schema so aggregate can derive the achieved set generically, the same open-world way SPEC-084 handles composability (knowledge lives with the party that has it).