
Fans several same-typed input streams t into one output of the same type, interleaving each value as it fires. Values pass through unchanged; this is a merge via merge_streams, not a join — inputs are not paired or zipped.
Aggregate several audio sources into one transcription stage.
Combine multiple alarm sources into a single JSON egress.
Fan replicated stage outputs back into one consumer, then log them.
t; merging differently-typed sources belongs in pack_union / unpack_union.