feat: guest (de)serialization for preprocessing & proof

[quangvdao]

Summary

Introduces a Jolt-owned guest encoding (GuestSerialize/GuestDeserialize) optimized for recursion verification, along with a native transport decode layer that converts compressed proof bytes into guest-optimized bytes.

Performance (recursion trace, virtual cycles, fibonacci)

Measured with:

• cargo run -p recursion --release -- generate --example fibonacci --workdir output
• RUST_LOG=info cargo run -p recursion --release -- trace --example fibonacci --workdir output

End-to-end deserialize costs (before → after)

• deserialize preprocessing: ~20,733,462 → 2,330,786 (≈8.9×)
  • generators (PCS::VerifierSetup): ~6,814,769 → 428,262 (≈15.9×)
  • shared/bytecode_preprocessing: ~13,896,414 → 1,882,027 (≈7.4×)
• deserialize proof: ~10,999,654 → 1,112,059 (≈9.9×)
  • joint_opening_proof (PCS::Proof): ~9,639,572 → 303,868 (≈31.7×)
• deserialize device: ~2,767 → 2,691 (about the same)

verification remains the dominant cost (~1.19B virtual cycles) and is unchanged by this PR.

Validation policy change (enabled by moving decode out of guest)

Previously, recursion verification deserialized arkworks-encoded proofs/preprocessing inside the guest using unchecked canonical deserialization (Validate::No) to save virtual cycles, meaning incoming curve points were not validated.

With this PR, transport bytes are decoded and validated in native execution (canonical deserialize_compressed, i.e. validated), and only then converted into the guest-optimized encoding. Because this validation happens outside the proved computation, it incurs no zkVM virtual-cycle cost.

Guest decoding remains intentionally unchecked (GuestDeserialize uses new_unchecked for field elements/curve points) because its input is now the trusted output of the native validation+conversion step.

Key Changes

Area	Change
guest_serde module	New GuestSerialize/GuestDeserialize traits encoding field elements as Montgomery limbs and curve points uncompressed - avoids expensive in-guest decompression/conversion
decompression layer	Native decompress_transport_bytes_to_guest_bytes() validates compressed transport bytes and emits guest-optimized encoding
Instruction encoding	Switched from JSON to fixed-width binary format for faster preprocessing decode
dory-pcs build	Made guest-safe by default; disabled disk-persistence APIs in non-host builds
cycle tracking	Gated behind cycle-tracking feature, enabled by default for recursion builds
code cleanup	Replaced fully qualified crate::zkvm::guest_serde::* paths with use statements

Motivation

Recursion verification requires deserializing proofs and preprocessing inside the guest. The standard arkworks encoding (compressed points, non-Montgomery field elements) incurs significant in-guest costs:

• Point decompression requires square root computation
• Field element conversion to Montgomery form on every deserialize

This PR eliminates those costs by pre-converting on the native side.

Testing

• cargo check -p jolt-core --features prover
• cargo clippy -p jolt-core --features prover
• Recursion example end-to-end test

Review Guidance

Focus on:

• jolt-core/src/zkvm/guest_serde.rs - the core encoding traits and impls
• jolt-sdk/src/decompression.rs - the native transport → guest conversion
• Dory impls in jolt-core/src/poly/commitment/dory/mod.rs

[moodlezoup]

@quangvdao can i close this?

[quangvdao]

Yes, it's badly outdated. We can revisit this in the future