Changelog of @hackage/data-sketches 0.4.0.1

Changelog for data-sketches

Removed dead pure-Haskell REQ internals that were superseded by the C backend in 0.4.0.0. No public API changes — insert, quantile, rank, countWithCriterion, and all other exports continue to work identically.
Dropped unused mwc-random, vector-algorithms, mtl, and hspec-junit-formatter dependencies.

HLL estimate is ~2.6x faster (C backend: ldexp replaced with bit manipulation; NEON/SSE2 intrinsics for merge and zero-counting).
Added estimate, merge, and query benchmarks for HLL, KLL, and Count-Min sketches (criterion suite).

Added countWithCriterion coverage: LT/LE threshold counting, boundary behavior at min/max, duplicate values, estimation mode, and non-finite exception handling.
Added quantile monotonicity tests: verifies quantile(r1) <= quantile(r2) for r1 <= r2 in exact mode, HRA estimation mode, and LRA estimation mode.
Added estimation mode capacity growth tests: 10K inserts with accuracy checks; batch vs sequential insert equivalence.

KLL Sketch (DataSketches.Quantiles.KLL): Quantiles with uniform additive error bounds (~1.3% at k=200). C backend, faster than Java DataSketches at small-to-medium N.
HyperLogLog (DataSketches.Distinct.HyperLogLog): Cardinality estimation. ~1.6% error with 4KB (p=12). C backend.
Theta Sketch (DataSketches.Distinct.Theta): Distinct counting with set operations — union, intersection, difference. C backend.
Count-Min Sketch (DataSketches.Frequencies.CountMin): Frequency estimation that may overcount but never undercounts. C backend.

Off-by-one in getCountWithCriterion: Binary search read past the active buffer region when spaceAtBottom=False (LowRanksAreAccurate mode), causing intermittent incorrect rank calculations from uninitialized memory.
growUntil in merge didn't loop: Only added one compactor level instead of recursing to the target. Silently dropped data from higher-level compactors when merging sketches with very different level counts.
Max value comparison inverted in merge: otherMax < thisMax instead of otherMax > thisMax caused the sketch to track the wrong maximum after merging.
compress captured compactors vector once: Replaced imapM_ over a snapshot with a loop that re-reads the vector each iteration, matching the Java implementation's dynamic size check.

Hedgehog property-based tests comparing Haskell outputs against Java DataSketches 6.1.1 reference. Exact equality in exact mode (no compaction); independent ground-truth validation in estimation mode.