Adds 6 hash-set builtins (make-hash-set, hash-set?, hash-set-add!,
hash-set-contains?, hash-set-size, hash-set->list). Same sentinel
scheme as hash-table but tag word = -2 (hash-table is -1, vector
is >= 0). One cons cell per entry (vs two for hash-table) since
a set stores keys only — that's where the speedup over the Scheme-
level vector-based ht-* lib comes from.
Benchmark (tests/bench-hashset.sh, via make bench-hashset),
N=5000, i5-8350U asm tier:
portable native speedup
insert ~130 ms ~7 ms ~20x
hit-lookup ~125 ms ~8 ms ~15x
miss-lookup ~240 ms ~12 ms ~20x
Portable is the ht-* lib from proof-netspace-server-lib.lsp
(vectors + cons chains + modulo, pure Scheme). Native replaces
the Scheme-level bucket walk with an asm loop that dereferences
pairs directly — no env lookups, no frame building per iteration.
All 137 asm + 189 functional (Python + C) tests still green.
russell@unturf.com
afb5616843