OptionalfilenameOptional source identifier for error reporting.
OptionalpreambleOptional sandbox-realm JS to run before the user source. The
preamble executes inside the same IIFE as the user code, so any
globalThis assignments persist for the read of __ifclite_ctx__
on the next line. Used by the test runner to inject synthetic
fixtures whose methods can't cross the realm boundary via
setGlobal.
Name of the entry function to invoke (e.g. "activate").