Function strays 

async fn strays(db: &Database, counter: u64, words: usize) -> u64

Counts shortroomid references with no forward row.

Purged rooms and losing allocations both produce them; no repair step touches a shortroomid family, so the count reports and gates nothing. Retained (unused) as the only in-tree measurement of the stray class, one restored call away from a repair that learns to act on it.