feat: kdf sync signer

[hlgltvnnk]

Summary by CodeRabbit

• New Features
  • Added support for asynchronous signing in wallet, WebAuthn, and MPC signing workflows.
  • Synchronous signing keys can now be adapted for use in asynchronous signing flows.
• Improvements
  • Signing and key derivation are now available through synchronous APIs where appropriate, while asynchronous workflows remain supported.
  • Updated wallet examples and signing integrations to reflect the available signing options.

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📥 Commits

Reviewing files that changed from the base of the PR and between 243bb7c and b809edd.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (16)

• contracts/wallet/signatures/ed25519/src/signer.rs
• contracts/wallet/signatures/webauthn/src/ed25519.rs
• contracts/wallet/signatures/webauthn/src/p256.rs
• crates/crypto/Cargo.toml
• crates/crypto/src/async_signer.rs
• crates/crypto/src/ed25519.rs
• crates/crypto/src/p256.rs
• crates/crypto/src/secp256k1.rs
• crates/kdf/Cargo.toml
• crates/kdf/src/ed25519.rs
• crates/kdf/src/secp256k1.rs
• crates/signatures/webauthn/src/ed25519.rs
• crates/signatures/webauthn/src/p256.rs
• crates/wallet/sdk/examples/mpc_sign.rs
• crates/wallet/sdk/src/lib.rs
• crates/wallet/sdk/tests/test.rs

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📥 Commits

Reviewing files that changed from the base of the PR and between c009270 and 243bb7c.

📒 Files selected for processing (6)

• contracts/wallet/signatures/ed25519/src/signer.rs
• crates/crypto/src/async_signer.rs
• crates/crypto/src/signer.rs
• crates/kdf/src/async_signer.rs
• crates/mpc/signer/src/lib.rs
• crates/wallet/sdk/src/lib.rs

🚧 Files skipped from review as they are similar to previous changes (2)

• contracts/wallet/signatures/ed25519/src/signer.rs
• crates/crypto/src/async_signer.rs

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📝 Walkthrough

Walkthrough

The change separates synchronous cryptographic and derived signing from asynchronous signer interfaces. It adds adapters and updates MPC, wallet, and WebAuthn implementations, examples, and tests to use the async interfaces.

Changes

Signing API transition

Layer / File(s)	Summary
Crypto signing contracts and adapters crates/crypto/src/signer.rs, crates/crypto/src/async_signer.rs, crates/crypto/src/{ed25519,p256,secp256k1,lib}.rs	Public-key access is separated from synchronous signing. Async signer traits and adapters are added. Curve implementations and signing test helpers use synchronous methods.
Synchronous derived-signing contracts crates/kdf/src/signer.rs, crates/kdf/src/{ed25519,secp256k1,schema/mod.rs}	DeriveSignerSchema separates schema and public-key derivation from synchronous signing. Ed25519 and secp256k1 implementations and round-trip helpers use the synchronous interfaces.
Asynchronous derived-signing interfaces crates/kdf/src/async_signer.rs, crates/kdf/src/lib.rs	Async derive-signing interfaces and implementations are added and exported. Their path parameters carry Send bounds at the trait or implementation level.
MPC asynchronous signing crates/mpc/signer/src/lib.rs	MpcOnChainSigner implements the async derive-signing and recoverable derive-signing interfaces, with schema handling in a separate implementation.
Wallet and WebAuthn async signer integration contracts/wallet/signatures/ed25519/src/signer.rs, contracts/wallet/signatures/webauthn/src/*, crates/signatures/webauthn/src/*, crates/wallet/sdk/{examples/mpc_sign.rs,tests/test.rs,src/lib.rs}	Wallet and WebAuthn wrappers require async signers. Examples and tests wrap signing keys with IntoAsync and use the async MPC interfaces.

Estimated code review effort: 4 (Complex) | ~45 minutes

Suggested reviewers: mitinarseny

Merge Risk: ⚪ Minimal · up to 243bb

No actionable issue is established for this signing API transition; it is mergeable after normal checks.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 70.15% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 67 functions across 23 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately identifies the main change: introducing synchronous signer support in the KDF APIs. It is concise and related to the pull request changes.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
In `@crates/crypto/src/async_signer.rs`:
- Line 17: Update the intra-doc link on `AsyncSigner::Error` to reference the
existing `sign_async` method instead of the nonexistent `sign` method, so
rustdoc resolves the link.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: 1b8b690c-1fbb-4178-bbfb-da8f6b594590

📥 Commits

Reviewing files that changed from the base of the PR and between 72c6688 and c009270.

📒 Files selected for processing (23)

• contracts/wallet/signatures/ed25519/src/signer.rs
• contracts/wallet/signatures/webauthn/src/ed25519.rs
• contracts/wallet/signatures/webauthn/src/mock.rs
• contracts/wallet/signatures/webauthn/src/p256.rs
• crates/crypto/src/async_signer.rs
• crates/crypto/src/ed25519.rs
• crates/crypto/src/lib.rs
• crates/crypto/src/p256.rs
• crates/crypto/src/secp256k1.rs
• crates/crypto/src/signer.rs
• crates/kdf/Cargo.toml
• crates/kdf/src/async_signer.rs
• crates/kdf/src/ed25519.rs
• crates/kdf/src/lib.rs
• crates/kdf/src/schema/mod.rs
• crates/kdf/src/secp256k1.rs
• crates/kdf/src/signer.rs
• crates/mpc/signer/src/lib.rs
• crates/signatures/webauthn/src/ed25519.rs
• crates/signatures/webauthn/src/mock.rs
• crates/signatures/webauthn/src/p256.rs
• crates/wallet/sdk/examples/mpc_sign.rs
• crates/wallet/sdk/tests/test.rs

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