refactor(fix): relocate bench_utils ckd functions

[gilcu3]

Closes #3633

[claude]

Pull request overview

Pure refactor: relocates prepare_ckd and PreparedCkdPackage out of bench_utils/frost_eddsa.rs (where they didn't belong, since CKD is a distinct protocol) into a new dedicated bench_utils/ckd.rs module, matching the per-protocol split established in #2634 for DKG / OT-ECDSA / robust ECDSA. Satisfies the acceptance criteria of #3633.

Changes:

• Created benches/bench_utils/ckd.rs containing the moved prepare_ckd and PreparedCkdPackage
• Registered the new module in benches/bench_utils.rs (mod ckd; + pub use ckd::*;)
• Dropped the now-unused ckd imports from benches/bench_utils/frost_eddsa.rs

Reviewed changes

Per-file summary

File	Description
crates/threshold-signatures/benches/bench_utils.rs	Registers the new ckd module and reexports it.
crates/threshold-signatures/benches/bench_utils/ckd.rs	New file housing prepare_ckd and PreparedCkdPackage (verbatim move).
crates/threshold-signatures/benches/bench_utils/frost_eddsa.rs	Removes the relocated functions and the now-unused confidential_key_derivation imports.

Findings

Verified:

• The moved function body is identical to the previous version (no logic drift).
• benches/ckd.rs is the only consumer of prepare_ckd / PreparedCkdPackage and continues to resolve them via bench_utils::prepare_ckd thanks to the pub use ckd::*; glob reexport — no import-site changes required.
• The remaining imports in frost_eddsa.rs (Rng, MockCryptoRng, generate_participants_with_random_ids, run_keygen, MAX_MALICIOUS) are all still used by the EdDSA prepare functions, so no further pruning is needed.
• No documentation references the old location, so no doc drift to fix.

No blocking issues. No non-blocking nits worth raising — the change is mechanical and tightly scoped.

✅ Approved

[Copilot]

Pull request overview

Refactors the threshold-signatures benchmark utilities by moving CKD-specific helpers out of the FROST/EdDSA bench-utils module into a dedicated CKD bench-utils module, aligning bench helpers with their respective protocols.

Changes:

• Removed prepare_ckd and PreparedCkdPackage from bench_utils/frost_eddsa.rs.
• Added a new bench_utils/ckd.rs containing the CKD bench preparation helpers.
• Registered and re-exported the new ckd module from benches/bench_utils.rs so existing bench consumers can continue importing from crate::bench_utils.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
crates/threshold-signatures/benches/bench_utils/frost_eddsa.rs	Removes CKD bench helpers that don’t belong to the FROST/EdDSA bench-utils module.
crates/threshold-signatures/benches/bench_utils/ckd.rs	Introduces a dedicated CKD bench-utils module containing prepare_ckd and PreparedCkdPackage.
crates/threshold-signatures/benches/bench_utils.rs	Registers bench_utils/ckd.rs and re-exports its public items via pub use ckd::*;.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[netrome]

Thanks!