UserContextMenuRegistry

Maps each user context-menu command name to its cache state. seedcord codegen populates this. It reads every command's toJSON() and emits a declare module '@seedcord/gateway' augmentation. keyof UserContextMenuRegistry is then the compile-time union of every registered user context-menu name. Never augment it by hand.

Kept separate from MessageContextMenuRegistry because Discord allows a user command and a message command to share a name, so a single name-keyed registry would collapse a legal pair.