refactor(GKR): Remove the Z/pZ assumption

[Tabaie]

This PR refactors the GKR codebase, in particular gate testing infrastructure and code generation, so that they accommodate extension fields.

NOTE: Pinning an unmerged gnark-crypto. Only to be merged after that.

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Note

Medium Risk
Changes Fiat–Shamir binding encoding (Marshal vs Bytes) and gate compilation metadata logic, which are security-sensitive for proof soundness; scope is broad across curves but heavily covered by existing GKR/sumcheck tests.

Overview
GKR is refactored so compilation, gate metadata, and Fiat–Shamir transcripts are not tied to prime fields only, paving the way for extension-field circuits.

Field model: CompileGateFunction, RawCircuit.Compile, gate registry, and gkrapi.API.Compile now take gkrcore.Field (with PrimeField(p) for F_p) instead of *big.Int. Gate degree/solvability testing runs over F_p[X]/(f) via an expanded gateTester, not plain mod-p arithmetic.

Transcript: Per-curve duplicate transcript types are removed; all curve GKR packages use gkrcore.NewHashTranscript with Challenge() / Bind() and element Marshal() (replacing Bytes() and getChallenge). resources.transcript is a pointer passed through prove/verify and BindGkrFinalEvalProof.

Codegen & tests: Generator templates and test-vector tooling switch small_rational → rational, unify setElement via big.Rat, and align fake-hash block sizing with Marshal. Benchmarks use Poseidon2; gkrtesting.NewCache takes a Field. gnark-crypto is bumped (PR note: depends on unmerged crypto).

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[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	golang/​github.com/​consensys/​gnark-crypto@​v0.21.1-0.20260913224755-1409fe592052 ⏵ v0.21.1-0.20261001213005-bfa51d3c359f	+1

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