How does Kaspa's KIP9 enforce block mass limits?

KIP9 introduces a `check_block_mass` function that verifies all transactions in a block fit within the block mass limit before the block is accepted. Every block in a blockchain acts like a container for transactions, and that container needs a size cap — without one, a miner could pack in so many transactions that most network nodes would struggle to keep up. KIP9's check runs the numbers and rejects any block whose contents exceed the allowed limit. For a Kaspa user, this means the network enforces a hard ceiling on how much any single block can carry, keeping the chain healthy and accessible to everyday node operators.