Given an array of pooled-buffer refs and a target budget, returns
the subset that should be evicted to bring total bytes ≤ maxBytes.
Strategy: sort largest-first and walk until the running total drops
under budget. JS sort is stable in modern engines (V8, JSC,
SpiderMonkey since 2019) so equal-size buffers retain their input
order — important for deterministic test output.
Pure selector for byte-budget eviction.
Given an array of pooled-buffer refs and a target budget, returns the subset that should be evicted to bring total bytes ≤ maxBytes. Strategy: sort largest-first and walk until the running total drops under budget. JS sort is stable in modern engines (V8, JSC, SpiderMonkey since 2019) so equal-size buffers retain their input order — important for deterministic test output.