State Sets

station:state_sets

The programme-state Sets — `set:station:state:warming_up`, `:on_air`, `:rebroadcast`, `:standing_by`. A programme is joined to exactly one; membership IS the state, and the ended membership stays readable as history rather than being deleted. The Sets hold PROGRAMMES only: they are populated by the station at run time and are declared here, not seeded, so a read of one never answers with the state atom itself.