feat: migrate bench tools to criterion harness

[moudyellaz]

🎯 Purpose

Migrate the two microbenchmark tools (crypto_primitives_bench and cycle_bench's verify path) from hand-rolled Instant::now() timing loops to the criterion harness. Gives statistical CIs, outlier flagging, and a richer comparison story for future PR gating.

⚙️ Approach

crypto_primitives_bench: replaced the custom timing loop with a criterion bench under tools/crypto_primitives_bench/benches/primitives.rs. The binary entry point is gone (no src/), the crate is now bench-only with harness = false.

cycle_bench: split into a library + binary so benches can reuse the helpers. The hand-rolled --verify CLI flag, --verify-iters argument, and run_verify(iters) helper are removed. A new criterion target at tools/cycle_bench/benches/verify.rs reuses prove_auth_transfer_in_ppe (extracted from the binary into the new cycle_bench library) to set up one PPE receipt outside the timed loop, then samples Receipt::verify(PRIVACY_PRESERVING_CIRCUIT_ID) under criterion's statistical sampler (sample_size 100, warm_up 2 s, measurement 15 s, noise_threshold 5%). Also aligns the auth_transfer call with the current authenticated_transfer_core::Instruction::Transfer { amount } enum API.

• Migrate crypto_primitives_bench to criterion (replace bin with bench target).
• Refactor cycle_bench into lib + binary; drop --verify CLI flag and run_verify helper.
• Add criterion verify bench for G_verify at tools/cycle_bench/benches/verify.rs.
• Add Justfile recipe just bench that runs both criterion targets.
• Update docs/benchmarks/cycle_bench.md and tools/cycle_bench/README.md.

🧪 How to Test

# Run the criterion benches locally:
cargo bench -p crypto_primitives_bench --bench primitives
cargo bench -p cycle_bench --features ppe --bench verify
# Or both via the Justfile recipe:
just bench

Criterion output lands under target/criterion/<group>/<bench>/. The cycle_bench verify bench runs one full PPE prove for setup (minutes) before the timed loop, so expect a long warmup on first run.

🔗 Dependencies

None.

🔜 Future Work

Add a bench-regression GitHub workflow that uses boa-dev/criterion-compare-action to gate crypto_primitives_bench regressions on PRs. The workflow needs the base branch to already have the criterion bench, so it ships as a follow-up after this PR merges.

📋 PR Completion Checklist

• Complete PR description
• Implement the core functionality
• Add/update tests
• Add/update documentation and inline comments

[Pravdyvy]

lgtm

[Arjentix]

Thanks for the PR, I like new approach. My main question is why not everything was moved to criterion? Also I can see that integration benches where not touched

[Arjentix]

Cool. Maybe also rename tools to benches?