Add i32 % execution tests for negative dividends across non-power-of-two moduli

[mstampfli]

The existing binary,i32_arithmetic:remainder cases draw operands from the sparse i32 range, whose only divisors are 10 and 256. That misses value-dependent codegen paths - e.g. modulus 768 - where some implementations compute signed % as if it were unsigned for negative dividends, returning 255 instead of -1 for -1 % 768.

This adds a remainder_negative test (and cache builders) exercising negative dividends (-1, -2, -5, -255, -256, -768, -769, -1000, -1234567) across moduli (3, 7, 100, 256, 768, 1000). Expected values use the existing i32_remainder_* reference helpers (truncated remainder, sign of dividend), unchanged.

The regenerated case cache (src/resources/cache/.../i32_arithmetic.bin + hashes.json) is included. npm run typecheck and npm run lint pass.

Context: discovered via the wgpu/naga OpSRem poison issue, gfx-rs/wgpu#8191.

[github-actions]

Results for build job (at 2992a57):

+webgpu:shader,execution,expression,binary,i32_arithmetic:remainder_negative:* - 16 cases, 16 subcases (~1/case)
-TOTAL: 283213 cases, 2325024 subcases
+TOTAL: 283229 cases, 2325040 subcases