Standard A2UI property bag (component-specific; see the mapping per type).
Optional
Pouchy-only reconstruction data for concepts A2UI has no standard for. A2UI renderers ignore it; fromA2UI() uses it to rebuild the exact node.
A2UI component type, e.g. "Text" / "Button" / "Row" / "pouchy/Progress".
Standard A2UI property bag (component-specific; see the mapping per type).