Constant MAX_CANDIDATE_POOL 

pub const MAX_CANDIDATE_POOL: usize = 1024;

Absolute ceiling on the query-time candidate pool, enforced in run regardless of the configured multiplier or how many entries a backend returns. Bounds the O(n^2) duplicate-collapse and MMR scans against a mis-sized config or a backend that ignores the requested recall limit (for example a no-embedding fallback that returns its whole list).