Set email preferences

Set how often the attention summary may arrive and whether optional product emails may send. Send at least one field. daily sends at most once a day and only on days something is actually wrong; weekly gathers anything still unresolved into at most one email a week; off stops it entirely. onboarding controls optional product emails. There is deliberately no MCP tool for this: these emails are how a person learns a post did not go out, and an agent that could switch them off could hide a failure it caused.