Build a non-canonical envelope where the payload doesn't fit the standard
{value} shape — e.g. Try.Failure carries {error: SerializedError},
Lazy-with-thrown-thunk carries the same.
Parameters
marker: string
The @functype type marker.
tag: string
The variant discriminator (may be the same as marker for
variant-less types).
fields: Record<string,unknown>
Additional payload fields merged into the envelope.
Build a non-canonical envelope where the payload doesn't fit the standard
{value}shape — e.g.Try.Failurecarries{error: SerializedError},Lazy-with-thrown-thunk carries the same.