### Added
- Added aggregation functions: `sum()`, `avg()`, `min()`, `max()`
- Added `groupBy()`, `having()`, `distinct()` query support
- Added `Agg` helper for inline aggregation in `select()`
- Added `tableExists` API to check whether a table is defined in the database schema (space‑agnostic)
- Added `query('table').exists()` chain API for efficient existence checks based on conditions without loading full records
- Added table schema TTL configuration and automatic expiration cleanup for time-based data
- Added pure memory mode (`ToStore.memory()`), providing ultra-high performance for scenarios like data caching, temporary computation, or diskless environments

### Fixed
- Fixed `count()` consistency with write buffer and index scan paths
- Fixed type cast error in aggregation return values

### Changed
- Changed license from MIT to Apache License 2.0
- Optimized `watch()` with adaptive debounce to coalesce high-frequency data change notifications, avoiding redundant re-queries under burst writes
- Optimized `batchInsert` insertion performance for large-scale batch write scenarios
- Optimized Windows performance