The "does value V declare method M; if so call it" decision was re-derived in a
dozen places with two different lookup helpers — records.ss jrec-cl and
collections.ss rec-coll-method were a byte-for-byte duplicate — and reduce only
honored a reify's own reduce method, not a deftype's:
(reduce + 100 (->Rng 5)) ; Rng deftype implementing IReduceInit
=> "not seqable" ; JVM: 110
Add iface-method / iface-call: one lookup that resolves a method for a deftype OR
a reify, with arity, and is the seam a core fn's interface arm collapses to.
jrec-cl now aliases rec-coll-method (the duplicate is gone). reduce routes its
IReduceInit arm through iface-method, so a deftype's reduce drives the reduction
like a reify's, reduced short-circuit included.
Runtime only, no re-mint. make test green (0 new/stale), +2 corpus rows.
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