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## Summary by CodeRabbit

## Release Notes

* **Configuration**
  * Added `ATLANTIS_DB_DRIVER` environment variable for database driver selection (defaults to SQLite).

* **Documentation**
  * Clarified dataset schema documentation for source configuration and mapping.
  * Updated pipeline documentation for improved gap-filling behavior across data sources.

* **Bug Fixes**
  * Fixed default dataset selection to validate against available datasets; falls back to first available if configured default is unavailable.

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