small fixes v15

[ivokub]

Collect different fixes.

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Note

Broad set of small but important fixes and cleanups across backends and std libs.

• Groth16 FFT kernels: remove duplicate twiddles[stage+1][1].BigInt calls before scaling a[7] in lagrange.go across all curves and the generator template
• PLONK prover: fix variable shadowing in getRandomPolynomial (all curves) and update template; minor test cleanups (remove redundant rebinds)
• Constraints API: optimize AssertIsCrumb with constant fast-path and single-constraint form in SCS; improved comments
• Conversion utils: make assertBytesLeq accept disallowEquality and enforce strict < modulus by default; update call sites and extend tests
• KZG verifier: correct generic type to GtElementT and constructor signature
• Recursion/PLONK verifier: handle zero public inputs; fix PI accumulation when no publics; add dedicated test; switch to std slices
• Emulated field/uints: use cmp.Ordered and slices.Max; guard empty polynomials; clearer hint error messages
• Misc: drop golang.org/x/exp in favor of std slices; remove dead code; add stats/snippets for AssertIsCrumb; doc/comment tweaks

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[Copilot]

Pull request overview

This PR collects various small fixes and improvements across the codebase, focusing on code modernization, bug fixes, and quality improvements.

Changes:

• Removed dependency on golang.org/x/exp by using standard library equivalents (slices, cmp)
• Removed unnecessary loop variable shadowing (Go 1.22+ style)
• Fixed PLONK verifier to properly handle circuits with zero public inputs
• Enhanced byte-to-native conversion functions with strict inequality checks
• Improved error messages and API documentation

Reviewed changes

Copilot reviewed 37 out of 38 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
go.mod, go.sum	Removed golang.org/x/exp dependency
std/recursion/wrapped_hash.go	Changed import from golang.org/x/exp/slices to slices
std/fiat-shamir/transcript.go	Changed import from golang.org/x/exp/slices to slices
std/math/emulated/field.go	Changed imports to use cmp instead of golang.org/x/exp/constraints, removed custom max function
std/math/emulated/field_mul.go	Added zero-term check and replaced custom max with slices.Max
std/compress/io.go	Removed custom min function in favor of built-in
test/assert_checkcircuit.go	Removed unnecessary loop variable shadowing
std/recursion/wrapped_hash_test.go	Removed unnecessary loop variable shadowing
backend/plonk/plonk_test.go	Removed unnecessary loop variable shadowing
std/recursion/plonk/verifier.go	Fixed handling of zero public inputs in PLONK verifier
std/recursion/plonk/verifier_test.go	Added test for zero public inputs case
std/conversion/conversion.go	Added disallowEquality parameter to assertBytesLeq for strict inequality checks
std/conversion/conversion_test.go	Updated tests for strict inequality checking
std/math/uints/hints.go	Improved error message formatting
std/commitments/kzg/verifier.go	Fixed type parameter from G2ElementT to GtElementT
std/accumulator/merkle/verify.go	Improved function documentation
frontend/cs/scs/api_assertions.go	Enhanced AssertIsCrumb with better error messages and comments
frontend/cs/r1cs/api_assertions.go	Enhanced AssertIsCrumb with constant handling and better comments
backend/plonk/*/prove.go	Fixed variable shadowing bug in getRandomPolynomial
backend/groth16/*/mpcsetup/lagrange.go	Removed duplicate twiddle assignment
internal/generator/backend/template/zkpschemes/plonk/plonk.prove.go.tmpl	Fixed variable shadowing bug in template
internal/generator/backend/template/zkpschemes/groth16/mpcsetup/lagrange.go.tmpl	Removed duplicate twiddle assignment in template
internal/stats/snippet.go	Added snippet for AssertIsCrumb
internal/stats/latest_stats.csv	Updated stats with AssertIsCrumb benchmarks

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