Distinguish no-GUID-at-capture from identity-no-longer-live; rewrite the drop
message to state the real recovery step; mark FX-GUID stability [verify — DAW];
guard mismatched fx/fxOffline lengths; the report never force-opens now.
view_state v2 writes identities beside the v1 slot array, so a downgrade keeps
what it had. An FX gone at restore time is dropped and reported, never restored
onto whatever took its place.
daniel