… refining IChainReader, and standardizing error handling

…contract; add tasks documentation for architecture remediation

- Updated RpcServer to include IChainReader and IChainWriter references.
- Changed SyncResponse structure to replace chunk_index with start_index.
- Enhanced NodeInstance to instantiate ChainService and pass it to PeerManager and BlockPropagation.
- Added ChainService tests to validate block submission and synchronization behavior.
- Modified block propagation tests to utilize ChainService for block handling.
- Implemented replaceChainStreaming in Blockchain to support streaming block replacement with validation.
- Updated peer discovery and management tests to accommodate ChainService integration.
- Adjusted sync tests to reflect changes in SyncResponse structure.

…ead of throwing exceptions