replaces the clear-when-full hashmap: at real-network scale (millions of DIDs) a full-cache wipe at capacity would cause a resolve stampede; LRU eviction degrades gracefully instead. zlay's util/lru.zig ported verbatim (thread-safe, O(1), holds 250k keys in production there) — its internal mutex also removes verify's own cache lock. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>