Effect LSM Memtable Compaction

A log-structured merge tree so random writes become sequential appends. Updating rows in place makes a write-heavy workload thrash on scattered seeks; an LSM appends every write to an in-memory memtable that flushes as one sorted immutable SSTable, so writes are sequential regardless of key order. Reads walk memtable then newest-to-oldest segment and stop at the first hit, and a delete is a tombstone that masks older values rather than a gap that lets them resurrect. Background compaction merges segments newest-first, dropping obsolete versions and tombstones to bound read cost. The demo proves newest-wins across segments and compaction collapsing three segments to one. Pinned to effect 4.0.0-beta.98.