0009. Pure helpers, generated elements and the Layer escape hatch

Superseded in part by 0018: the vocabulary is a skeleton for footage and time; anything visual may be free code in a <Layer>.

Context

A fixed vocabulary (0002) must not stop the model from abstracting (a lower third used in three places) or from doing what the vocabulary cannot say (a counter, a chart, a custom animation).

Decision

Helpers are pure functions of their props and are expanded by the resolver. Elements a helper produces are literal when the helper is used once, and generated when it is used more than once or inside a loop; the editor bakes a generated element into literals before the first gesture on it. <Layer> holds arbitrary React; its interior is opaque to the editor, driven by useT() for progress, and the editor asks the model to change it. Hooks other than useT in helpers are a lint error.

Consequences

• Abstraction is allowed and the cost (a bake) is paid only when the user edits one copy.
• The resolver needs no React runtime: it calls helpers as functions.
• Layer interiors need the evaluated element at render time, which the player takes as a prop; the kit does not keep them.