refactor: use canonical types from contract interface in test-parallel-contract

[pbeza]

Replace locally-redefined Payload, SignRequest, SignArgs, and CKDRequestArgs with canonical types from near-mpc-contract-interface, resolving the TODO(#1057) in test-parallel-contract.

Closes #1057

[claude]

Code Review: refactor test-parallel-contract to use canonical types (#1057)

Clean refactor that replaces locally-defined types with canonical ones from near-mpc-contract-interface. Verified:

• Serialization compatibility: Old Payload used #[serde(rename_all = "PascalCase")] + String; canonical Payload uses default PascalCase enum variants + hex_serde on BoundedVec<u8> — both produce identical JSON (hex-encoded string under "Ecdsa"/"Eddsa" keys).
• Field optionality: Old code had Option<Payload> / Option<u64> but always passed Some(...); canonical types are non-optional — no behavioral change.
• CKDAppPublicKey wrapping: Correctly wraps Bls12381G1PublicKey in CKDAppPublicKey::AppPublicKey() to match the canonical enum.
• .try_into().unwrap() on SHA-256 output (always 32 bytes) converting to BoundedVec — safe since the size is guaranteed to match ECDSA_PAYLOAD_SIZE_BYTES. This is test contract code, so unwrap is acceptable per project conventions.

No critical issues found.

✅ Approved

[Copilot]

Pull request overview

Refactors test-parallel-contract to reuse canonical signing/CKD request types from near-mpc-contract-interface, eliminating locally duplicated request/payload structs and aligning the test contract’s JSON arguments with the shared interface.

Changes:

• Replace locally defined Payload, SignRequest, and CKDRequestArgs with near_mpc_contract_interface::types::{Payload, SignRequestArgs, CKDRequestArgs, DomainId, CKDAppPublicKey}.
• Update payload construction to operate on raw bytes (SHA-256 output) rather than pre-hex-encoded strings.
• Remove the hex dependency from test-parallel-contract (and corresponding lockfile entry).

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 1 comment.

File	Description
crates/test-parallel-contract/src/lib.rs	Switch to canonical interface types for sign/CKD args and adapt payload/domain_id construction accordingly.
crates/test-parallel-contract/Cargo.toml	Drop unused hex dependency after moving to interface Payload serialization.
Cargo.lock	Remove hex from test-parallel-contract dependency list.

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[gilcu3]

Thank you!