Maintain the project's durable design memory — vision, pillars, MVP scope, and a decision log with reasons and evidence — so settled calls stay settled and rejected ideas stay rejected across sessions. Use when a design or scope decision gets made or overridden, when an idea is rejected or killed, when the user asks "didn't we already decide this", when starting work that should be checked against prior decisions, or when setting up a new game project's vision and pillars.
