0002. A fixed vocabulary with literal ids

Superseded in part by 0018: the vocabulary is a skeleton for footage and time; anything visual may be free code in a 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

Context

If the file is the edit (0001), the editor must be able to find an element from a gesture, change one value, and leave the rest of the file alone. Free React cannot be read that way: a <div> that happens to show a clip is not addressable, and its timing is wherever the author computed it.

Decision

The file is written in a fixed vocabulary (<Composition>, <Track>, <Clip>, <Title>, …, 26 elements) whose props are Zod schemas. Every element carries a literal id, unique in the file. Timing props (in, out, duration, start, offset, anchor, at) are literals or time references. A collection the inspector edits one by one (keyframes, effects, captions) is child elements, not a prop array. A lint enforces all of this.

Consequences

• Gestures, undo, the model's search-and-replace and the preview's data-el attributes all address elements by the same id.
• The resolver can place everything without executing user code beyond pure helpers; the vocabulary components render nothing themselves.
• The model gives up some freedom; the prompt and the lint tell it exactly what it gave up and why.

Alternatives

Stamping ids at compile time when missing (Diffusion Studio does this): works, but makes the first save rewrite the author's file. We prefer the lint error and a model that writes ids itself. Structural addressing by position: breaks on every insertion.