Auto resolve conversations after n days of inactivity

Editor assessment

The subject states a real feature, conversations auto-resolve after a configurable number of inactive days, with the 'n days' phrasing honestly signaling a parameter, and feat is right. The 'fixes: #418' footer is well-formed token-value grammar linking to the long-standing request. But no body explains the default, whether resolutions are silent, and how auto-resolution interacts with pending conversations, the operational questions an administrator must answer before enabling it. No scope. Hygiene otherwise fine. Understandable, valid, and thin on policy. The default policy and its reach are undocumented.