OptionalexecutionWhere the operation came from: the host's declared
EXECUTION_KINDS value projected onto the reported vocabulary,
or other for a kind outside it. Absent when the host declared none.
The JavaScript runtime the engine inferred for itself, matching the
executionContext.runtime the same operation stamps on its history
entries.
The caller-provenance fields every engine event payload carries: the engine's own view of the host that invoked it.
ExecutionContext.idis never reported.