Constant STATE_HISTORY 

pub const STATE_HISTORY: &str = "state_history";

State-history journal column family: [u8; 8] => Vec<u8>

• [u8; 8] = block_number.to_be_bytes() (big-endian so lex order == numeric order)
• Vec<u8> = JournalEntry::encode()

Stores one reverse-diff entry per committed block, enabling reorgs deeper than the in-memory TrieLayerCache. Pruned at finality.