Function is_stream_decision 

const fn is_stream_decision(kind: ActionKind) -> bool

Whether this kind is one of the four StreamAction decisions.

The compiler does not check this list. It is a matches!, not an exhaustive match, so a StreamAction variant left out of it silently becomes NotAttemptable { SiteReturnsStreamAction } at Site::StreamOpen and Site::StreamHeader — the published table then says a site’s return type rules out a variant of that very return type. tests/action_matrix.rs::the_published_table_and_classify_agree is the gate that catches it, because its hand-transcribed twin of this list is written independently.