Rename the KmerPartition type to KmerPartitions across obikindex, obikpartitionner, and obikphylo/siblings to reflect an updated data model. Update the Mat enum in siblings/cache.rs to add a SparsePresence variant and simplify opening logic by delegating sparse versus dense detection to PersistentBitMatrix. Apply consistent code formatting, import reordering, and multi-line refactoring throughout the affected modules.
Replaced scattered direct metadata loading with centralized instance methods on `KmerPartition` to guarantee consistent error mapping and legacy recovery. Introduced `StorageKind`, `LayerContent`, and `EvidenceKind` enums alongside lightweight disk-probe methods that inspect file presence without opening heavy data structures. Updated callers across the index, partitioner, and phylo modules to use the new partition API, and added unit tests validating the introspection behavior.
Introduce a design specification outlining performance bottlenecks in layer data access and an agreed-upon implementation direction for caching. Refactor the codebase to centralize index and layer directory path resolution within the partition object, replacing manual string joining and external helper functions with dedicated accessor methods.
Eric Coissac