empty, assoc-in, and update-in move to 20-coll.clj as the canonical recursive
ports; interpose and take-nth move to the lazy tier WITH their canonical
transducer arities (volatile-based), so the seed's td-interpose/td-take-nth
helpers go too. (empty lazy-seq) is () now — the kernel fn returned a bare
host table for it.
keys/vals/empty? stay put for now: they're expander-coupled — 00-syntax's
when/and/or/cond/destructure expanders call them at expansion time, which
happens during the kernel-tier compile, before any later tier exists. They
move when early defns get the staged-recompile treatment macros already have.
26 new spec rows (incl. transducer arities through sequence/into and laziness
checks against (range)). Gate green: conformance 326x3, suite >= baseline,
full jpm test.
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