nimiq-blockchain CVE-2026-46543

The affected component is the nimiq-blockchain Rust crate (pkg:rust/nimiq-blockchain) within the Nimiq Albatross proof-of-stake consensus implementation (core-rs-albatross). The root cause is CWE-617 (Reachable Assertion): Rust's panic mechanism - invoked either via an explicit panic! or via .expect() on a Result - can be triggered by attacker-controlled input. The RequestBatchSet message handler calls get_epoch_chunks, which iterates backward through macro blocks via Policy::macro_block_before. That function unconditionally panics when called with the genesis block number, as there are no macro blocks before genesis. Additionally, two prove_num_leaves calls used .expect('Failed to prove history size') rather than proper Result propagation, meaning any failure in those paths also crashed the node process. PR #3745 applies two fixes visible in the diff: a boundary guard (if prev_macro_block_number <= Policy::genesis_block_number() { break; }) added to chain_store.rs to halt backward iteration at genesis, and conversion of .expect() calls in consensus/src/messages/handlers.rs to graceful error returns using the ? operator with the new BatchSetError::CouldntProduceHistorySizeProof variant.