In the DraftCXU data model, `cxu_id` is a string formatted as `1220` plus a SHA-256 hex digest with 68 characters so that each draft context unit has a deterministic identifier format.

cxu_id: str # "1220" + SHA-256 hex (68 chars)

— PYRANA_PLATFORM_ARCHITECTURE_REFERENCE.md

DraftCXU:

— PYRANA_PLATFORM_ARCHITECTURE_REFERENCE.md

"1220" + SHA-256 hex (68 chars)

— PYRANA_PLATFORM_ARCHITECTURE_REFERENCE.md