What is header pruning and why does Kaspa need it?

Header pruning is a planned Kaspa consensus feature that will keep a node's database size nearly fixed over time, even as the network keeps growing. Without it, a long-running node accumulates data indefinitely, and the current workaround is to periodically resync the node from scratch — essentially wiping and re-downloading. The Rust rewrite roadmap includes header pruning as a new consensus-level feature so that nodes can run for long periods without that maintenance burden. For anyone who wants to run their own Kaspa node, this matters because a stable database size makes the hardware and storage costs predictable and manageable.