noun: Lagoon %int2 comparison + reduction array jets

[sigilante]

Stacked on #1047. Hoon/master side: urbit/numerics#67.

Extends the Lagoon array jets with %int2 cases beside %i754 for the comparison and reduction ops (no GEMM):

• gth/gte/lth/lte — per-lane signed (two's-complement) compare → 1/0 ray.
• cumsum — full wrapping sum → scalar ray.
• dot — sum of products (wrapping) → scalar ray.
• min/max — extremum by two's-complement order → scalar ray.
• argmin/argmax — forward ravel-index of the first extremum (bare index).

Native per lane (8…128-bit, no GMP); signed compares reinterpret the lane as the matching signed C type. Scalar reductions box via a _la_scalar_box helper = +scalar-to-ray's shape (all-1s of the input rank).

Also fixes the i754 reduction-jet result shape (carries urbit/numerics#68 into the runtime): cumsum/min/max/dot shared the same _la_scalar_box helper, replacing the prior hardcoded ~[1 1]/~[len 1]/~[1] that only matched one rank — a silent jet/Hoon mismatch on the boxed meta. trace (always rank-2) and diag (returns a vector) are correct as-is.

Verified jet == numerics Hoon on a hoon-135 fakezod across native widths incl. 128-bit, ties, and negatives — for both %int2 and (now) %i754 reductions.

🤖 Generated with Claude Code

[sigilante]

Rebased onto #1047 (base retargeted to sigilante/twoc-jets), so this PR is now just the %int2 comparison/reduction commit. The %int2 cases (gth/gte/lth/lte, cumsum/dot/min/max/argmin/argmax) slot into #1057's rewritten comparison and reduction wrappers; the +dot case was added by hand to #1057's restructured (unifying-equality-safe) dot wrapper, which the auto-merge could not place. All _la_int2_* helpers and int2 wrapper results are typed u3_weak; _la_int2_box (which transfers r_data into the boxed ray) carries @Refcount: transfers r_data`` so the reduction wrappers do not read as leaking it (refcount linter, #1059).

#1048's separate i754 reduction-shape fix is dropped — #1057 already boxes those with the all-ones-of-rank +scalar-to-ray shape (_ones_shape), which the %int2 box matches.

Verification: builds clean at both loom widths (-Werror); linter reports 0 findings on lagoon.c (strict-weak). lagoon-int2 (5 arms: modular wrap, signed div/rem, abs, comparison convention, cumsum) and twoc (13 arms) run green jetted for both binaries. Merge order: #1057, then #1047, then this.