v4.2.0

Added

• comparator-aware range tombstones (#180)
• (compression) CompressionProvider trait + pure Rust zstd backend (#176)
• (error) RouteMismatch error, blocked_bloom cleanup, bench/clippy fixes (#166)
• (config) per-level Fs routing for tiered storage (#163)

Performance

• (bench) consolidate benchmarks + nextest + flamegraph pipeline (#175)

Testing

• (table) add zstd dict helper coverage (#181)