BlueprintRef interface
Identifies a blueprint tar — opaque to Manager, resolved by the worker at launch time. sha256 is the canonical cache key (lowercase hex of the tar’s SHA-256). The same tar may arrive via different transports (URL, inline bytes, content-addressed lookup) but its cache entry is one and the same.
See .ai/steve/tasks/39-blueprint-jobs.md for the full design.
Signature:
export interface BlueprintRef