state transition function

[turuslan]

• implement stf from spec
• simple unit test for stf

[Copilot]

Pull Request Overview

This PR implements the state transition function (STF) from the lean Ethereum specification, enabling block validation and state updates in the blockchain system.

Key changes include:

• Implementation of the complete state transition function with block processing, slot advancement, and attestation handling
• Addition of SSZ serialization support to core data structures (State, Config, BlockBody)
• Creation of comprehensive unit tests to validate the STF implementation

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/unit/blockchain/state_transition_function_test.cpp	Unit test validating STF with genesis state generation and multi-block transitions
tests/unit/blockchain/CMakeLists.txt	Build configuration for new STF test
src/types/state.hpp	Updated State struct with SSZ serialization and proper field types
src/types/config.hpp	Added SSZ serialization to Config struct
src/types/block_body.hpp	Renamed votes to attestations and updated to use SignedVote
src/types/block.hpp	Modified setHash() to allow re-setting with validation
src/blockchain/state_transition_function.hpp	Interface definition for STF with error handling and processing methods
src/blockchain/state_transition_function.cpp	Complete STF implementation with block processing, justification, and finalization logic
src/blockchain/is_justifiable_slot.hpp	Utility function to determine valid justifiable slots using mathematical conditions
src/blockchain/CMakeLists.txt	Build configuration updates to include new STF source file

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