[cadence d4253b6d859add66] A phase declaration can move a story without removing it from its previous phase's story list. #280

Raised at crates/baley-core/src/scope/roadmap.rs:185 as medium by openai, ruled refuted.

Claim. A phase declaration can move a story without removing it from its previous phase's story list.

Failure scenario. Starting from approved_s1, apply phase.declared for phase 2 with stories [1, 2]. This branch sets story 1's phase to 2, and phase 2 lists [1, 2], but phase 1 still lists [1]. The projector accepts the event and produces contradictory membership: both phases claim story 1. It must remove the old membership or reject the overlapping declaration rather than partially applying the move.

Filed by Cadence. Fingerprint d4253b6d859add66 over (file, claim).