Pins down what a transient is in Jolt (tagged table over a native Janet
array/table, canonical-keyed for maps/sets), where behavior deviates from the
JVM (O(n) transient/persistent! edges with O(1) native ops between, no
owner-thread check — same as Clojure 1.7+, transient-of-list leniency), and
the three reasons the machinery is seed-resident rather than a migration
candidate: it IS the mutation kernel, it sits under the seed's own dispatch,
and the value layer is declared irreducible. Exists so the kernel-shrink
ladder (jolt-tzo) doesn't revisit transients every round.
