Interface: AssetRef

A reference to bytes held in DeckIr.assets, standing where a write-API option wants image/media data. Printed as a path or an inline data: literal depending on the print options — an IR-level decision would bake one choice into the IR and force a re-read to change it.

The $asset sigil is deliberate: no write-API option object has a $-prefixed key, so a value carrying one is unambiguously a reference rather than user data.