* revert: use masternodes from snapshot to verify vote
* fix underflow during chain initialization
* add previously removed test
* rename snapshot > snap for consistency
Previously, vote verification would log errors and fail when the referenced block header was not yet available locally, especially when nodes in the same round processed votes before receiving the block header. This commit changes the logic to defer verification and log at debug level if the header is missing, preventing unnecessary error logs and aligning with upstream geth behavior for out-of-order message arrival during consensus voting.
