Delta Grows Up: Writes, Unity Catalog and Time Travel

DuckDB's Delta and Unity Catalog extensions have graduated from experimental status. Key additions include INSERT support for Delta tables (with atomic multi-statement commits), time travel queries via VERSION and PIN_SNAPSHOT options, and full Unity Catalog integration supporting both OSS and Databricks UC. Catalog Managed Tables (CMT) enable coordinated concurrent writes across multiple engines, with UC acting as a commit arbiter to prevent conflicts. Incremental snapshot loading is also coming in v1.5.3, significantly speeding up time travel across nearby versions. UPDATE, MERGE, and DELETE support and DDL for table creation are on the roadmap.