CACHE_ SCHEMA_ VERSION
Version of the cache directory schema. Bumped whenever the on-disk layout (file names, meta-file shape, or ModelDescriptor JSON structure) changes in a way that would mis-deserialize older entries.
Version history: 1 — initial cache layout. 2 — ModelDescriptor schema change: removed description; replaced experimentRunParameters: ExperimentRunParameters with experimentRunDefaults: ExperimentRunDefaults (no runtime- identification fields).