The IR compiler tested jump targets and cursor indices with the
polymorphic (<) and (=). Both types are Vdbe's, so the call sites were
reaching past the module that owns them to compare on representation.

Vdbe now exposes compare_label and equal_cur, and the row-dedup and
group-filter paths call Value.equal instead of structural (=)/(<>) on a
Value.t -- Value.equal compares floats by bit pattern, which structural
equality does not.

These packages are published only to the opam overlay, not the public
opam-repository. Without the repo-add line a reader who runs opam install
gets nothing and has to hunt down the overlay URL by hand.

run_precompiled's sort comparator defined its key-walk [go] inside [cmp r1 r2],
so [go] closed over r1/r2 and a fresh closure was allocated on every one of the
O(n log n) comparisons stable_sort makes (1.9M allocs x 64 B = 114 MB on the
sqlite bench).

Take the two rows as explicit arguments so [go]'s closure is built once -- it
now captures only the loop-invariant keys/nout/collate -- and each comparison is
a full application with no allocation. Same comparison logic and order; this is
the shared query VM, so sqlite/catalog/parquet ORDER BY all benefit. 60 catalog
+ 28 sqlite tests pass.