pub const MAX_CHAIN_DEPTH: usize = 4; // 4usizeExpand description
How many chained levels a single write may cascade through.
A derived edge written by one rule can feed a via-hop rule, whose derived edges can feed another, and so on. Chaining stops after this many levels even if further rules would still fire, so one write is always bounded. Cycles are rejected at rule-creation time; the cap bounds long acyclic chains and any chain the creation-time check could not see (a rule created in an earlier release, or a same-batch rule window).