Base coordination type for Blue event payloads. An Event is a Blue node that may be placed in a Timeline Entry, emitted by a workflow, routed through a channel, or recorded for audit. Event itself defines no operation semantics; concrete event types such as Operation Request, Chat Message, Status Change, Customer Action Requested, or domain events provide the fields that processors and handlers understand. Events are passive content. A Blue Contracts processor treats delivered event nodes as read-only. Matching, adaptation, authorization, and side effects are defined by channels, handlers, workflows, and policies. Because event nodes are Blue content, their exact fields, values, names, and descriptions participate in identity when they are hashed or stored.