Constant CACHE_RAM_UNKNOWN_KV_ALLOWANCE_BYTES 

pub const CACHE_RAM_UNKNOWN_KV_ALLOWANCE_BYTES: u64 = _; // 8_589_934_592u64

KV allowance assumed when the model’s metadata doesn’t permit an estimate. Deliberately generous: over-reserving shrinks the cache (safe), whereas under-reserving risks memory pressure.