Adapts a homogeneous stream of one kind to another, using convert. When
fromKind === toKind the stream is passed straight through untouched (no
per-chunk work at all). This is the ONE place a kind mismatch is decided -
once per stream link, not once per chunk.
Adapts a homogeneous stream of one kind to another, using
convert. WhenfromKind === toKindthe stream is passed straight through untouched (no per-chunk work at all). This is the ONE place a kind mismatch is decided - once per stream link, not once per chunk.