Sparse delta-file snapshots with copy-on-write in the flusher.
Zero write-path overhead when no snapshot is active.
New: snapshot.go (SnapshotBitmap, SnapshotHeader, delta file I/O)
Modified: flusher.go (flushMu, CoW phase in FlushOnce, PauseAndFlush)
Modified: blockvol.go (Create/Read/Delete/Restore/ListSnapshots, recovery)
Modified: wal_writer.go (Reset for snapshot restore)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>