Refactor SDK to Support Multiple Protocols (Hashchain and Signature/Multisig)

[pali101]

Description

Currently, SDK code and types are named generically for the hashchain protocol. With the new signature/multisig channel contract, we need to segregate logic and types for each protocol to ensure clarity, maintainability, and scalability.

Tasks

• Rename and move hashchain types to /src/types/hashchainChannel.ts
• Add types for signature/multisig protocol to /src/types/signatureChannel.ts
• Split protocol classes: HashchainProtocol (/src/hashchainProtocol.ts), SignatureProtocol (/src/signatureProtocol.ts)
• Update index.ts to export both protocols and type groups
• Ensure ABI and utils are clearly organized for both protocols

Goal

Clear separation and naming for each protocol, making SDK ready for future extensions.