List Discord guild members

Cursor-paginated list of guild members. Returns Discord's raw member objects so callers can build community-ops automation (e.g. "add role to all members joined in the last 7 days") on the actual platform shape.

Pagination: pass after = the last user.id from the previous page. Omit on the first call. Response includes a nextCursor and hasMore flag so callers don't need to know Discord's pagination shape.