Treat merge plans as shared expiring work

Context

Current workspace access and retention differ from the documented creator-only design.

Decision

Current plans are shared with qualified workspace administrators, record attributed answers, expire at their stored instant and remain retained after settlement.

Alternatives Considered

Limit changes to the creator. This prevents direct handover; Product has not resolved the competing access choices.

Delete settled plans after seven days. The documented cleanup is absent and needs an explicit retention implementation.

Consequences

Colleagues can edit plans and refresh their approval boundary. Settled plans retain working snapshots of personal information. Current expiry counts from creation rather than the approved last-change rule.