Dementia and Mild Cognitive Impairment in Prison (DECISION) care pathway and training package: protocol for a realist-informed mixed-methods feasibility study. - Forsyth K; Buck D; Stalker K; Allgar V; Shaw J; Cowley-Sharp R; Hunter R; Lennox C; O'Neill A; Robinson C; Ware S; Robinson L (BMJ open, 2026)