feat: make Jolt verifier panic-free

[quangvdao]

Summary

Harden the Jolt verifier to return Result<_, ProofVerifyError> instead of panicking on malformed proofs or invalid inputs. This is critical for production use where verifier crashes could be exploited.

Status: ✅ Complete — all 395 jolt-core tests pass

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Changes

Core verifier hardening (verifier.rs)

• Add early validation in JoltVerifier::new() for trace_length, ram_K, bytecode_K
• Use checked_next_power_of_two() to prevent overflow panics
• Replace slice indexing with .get() + proper error returns
• Replace zip_eq with length validation + zip
• Replace HashMap::remove().unwrap() with ok_or_else()
• Fix serialization methods to propagate errors

Transcripts (blake2b.rs, keccak.rs)

• Make challenge_bytes() panic-free using iterator-only access
• Use guarded split_at_mut() and safe zip() instead of indexing

Opening accumulator (opening_proof.rs)

• Refactor OpeningAccumulator trait to return Result
• All get_*_opening and append_* methods now return Result<_, ProofVerifyError>
• Add typed error variants: MissingCommittedOpening, MissingVirtualOpening, MissingAdviceOpening

Sumcheck verification (sumcheck.rs, sumcheck_verifier.rs)

• Add empty check before .max().unwrap() calls
• Make SumcheckInstanceVerifier trait methods return Result
• Propagate errors through verify() and cache_openings()

Claim reductions (claim_reductions/*.rs)

• All verifier-side new() constructors return Result
• Remove verifier-reachable unwraps on 2.inverse() and optional fields

Spartan/RAM/Registers verifiers

• shift.rs: Remove try_into().unwrap() in ShiftSumcheckParams::new
• ram/mod.rs: remap_address now returns Option instead of panicking
• output_check.rs: Verifier returns errors instead of unwrapping remap_address

Dory PCS mitigation (external dependency)

• Resample transcript challenges if zero (prevents inv().expect() panics)
• Wrap dory::verify in catch_unwind to convert panics to ProofVerifyError::DoryError
• ⚠️ Note: catch_unwind only works in panic=unwind builds

Error types (errors.rs)

• Add typed variants: CountMismatch, SliceTooShort, ClaimMismatch, AddressRemapFailed, FieldArithmeticError, MissingProofComponent
• Remove catch-all InvalidProofStructure(String)

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Scope

• ✅ Verifier code paths — fully hardened
• ⏸️ Prover code paths — intentionally unchanged (out of scope)
• ⚠️ External dory-pcs — mitigated via catch_unwind, but full panic-free guarantee in panic=abort builds would require patching upstream

[0xAndoroid]

Code Review Finding

File: jolt-core/src/subprotocols/sumcheck.rs:285

assert_eq!(self.compressed_polys.len(), num_rounds);

This assert_eq! remains in SumcheckInstanceProof::verify() and will panic if a malformed proof contains the wrong number of round polynomials. This contradicts the PR's goal of making the verifier panic-free.

Suggested fix:

if self.compressed_polys.len() != num_rounds {
    return Err(ProofVerifyError::InvalidRoundCount {
        expected: num_rounds,
        actual: self.compressed_polys.len(),
    });
}

Note: The InvalidRoundCount error variant already exists in ProofVerifyError.

[0xAndoroid]

Looks good to me, except for some nits that I mentioned.
I'm okay with merging in right now, though it might cause quit e a bit of conflicts with ZK implementation. I think it shouldn't be too harsh tho

[quangvdao]

I'm just putting this PR up for now, I think it still requires a fair bit of plumbing & cleaning up (esp. on panic freedom on Dory side).

I'm okay with letting this one stay up for a while until it's fully done. Can merge main into this occasionally and fix any problems.

[0xAndoroid]

Dory verifier is panic free (that's what @markosg04 said)