conj/assoc/dissoc/disj/pop/into and empty now thread the receiver's
metadata onto the result, matching Clojure (each op constructs a new
collection with meta() carried forward; coll.empty() is
EMPTY.withMeta(meta())). The metadata side-table is now weak so meta on
intermediate collections is reclaimed with them, and empty-list-t carries
an (unused) field so a metadata-bearing () is a distinct identity from the
shared singleton instead of leaking meta onto every ().
Unblocks metadata-driven walks (aero/integrant): (into (empty form) ...)
now preserves a vector/map/set's metadata, so a postwalk whose outer fn
reads (meta x) sees it.
The 1123-line collection tier is the largest source file. Cut it at two existing
section banners into 20-coll (predicates, printing, hierarchies, pure-over-core
leaves), 21-coll (rand/sort seams, the test runner, fn combinators), and 22-coll
(canonical Clojure ports, transduce/into, JVM-shape stubs). No macros in this tier,
so order is the only constraint; the emit-image manifest lists the three in
sequence. Re-minted seed is identical apart from gensym label renumbering.
