noun: /lib/twoc two's-complement jets (scalar + Lagoon %int2 arrays)

[sigilante]

Bit-exact C jets for the numerics /lib/twoc two's-complement integer library, under the non chapter alongside math/lagoon/unum. Hoon side: urbit/numerics#66.

No vendored library — the arithmetic is plain integer C plus GNU MP (already linked into pkg/noun).

Changes

• jets/i/twoc.c — one %twid core (the width-keyed door where /lib/twoc keeps its logic; the bloq-keyed facade re-exports its gates, so this fires for both call paths). Reads wid from the door sample (gate axis 30) and dispatches: native c3_d for wid<=64, __int128 for <=128, GMP (u3r_mp/u3i_mp) for >128. Arms: add sub neg mul div rem pow abs gth lth lte gte. Declines to Hoon on out-of-width operands and zero divisors.
• jets/i/twoc.h — shared two's-complement kernels (used by twoc.c and lagoon.c).
• jets/i/lagoon.c — the element-wise array jets (add/sub/mul/div/mod-rays) gain a %int2 case beside %i754, looping native two's-complement per lane over the ray byte buffer (one C pass vs the super-linear Hoon bit-packing loop).
• jets/w.h, q.h — u3wi_twid_* / u3qi_twid_* declarations.
• build.zig — add jets/i/twoc.c (no new linkLibrary; GMP already linked).
• jets/{135,136,137}/tree.c — register twid under non (sibling of lagoon).

Validation

• Standalone vs an independent reference: 8280 native + 5692 GMP checks pass.
• Fires bit-exact on a hoon-135 fakezod. Scalar proven two ways (a planted sentinel confirmed the C path executes via both twid-direct and the twoc facade; timing toggle ~3.3×). %int2 array ops verified jet == Hoon for all five; ~310,000× over interpreted at 200k lanes.

Built and fired on the 32-bit runtime.

🤖 Generated with Claude Code

[sigilante]

Coordination note: #1057 rewrites the lagoon.c validation layer and several kernels on develop, and every wrapper this PR's %int2 additions hook into changes shape there (_check takes [meta data] borrowed — the u3nc call sites leak — plus added consistency checks and NaN-correct comparisons). After #1057 lands, this branch's lagoon.c should be rebuilt on top of it; the numerics repo's lagoon/vere/noun/jets/i/lagoon.c (urbit/numerics#75) is exactly that combination (int2 + the #1057 fix set), compile-verified — modulo its desk-specific %mod semantics, which upstream should not take.

🤖 Generated with Claude Code