scene

The Mix Scenes document core, with no renderer and no interpreter. A scene is a --- envelope of headers followed by one ```mix fence holding a strict-data map of nodes:

---
scene: 1
name: about-panel
citizen: about-citizen
model: {"title":"About"}
---
```mix
root: {widget: "column", gap: 8, children: ["title"]}
title: {widget: "text", text: "= $model.title", size: 18, bold: true}
```

The crate provides:

• parse to a SceneDocument, lint for every diagnostic (codes in ALL_CODES), resolve to a ResolvedScene with defaults filled and bindings evaluated, diff between two resolved trees, describe for a family's ports, and to_source to write a document back out;
• bindings: = expression ports compiled once (compile), re-evaluated on a model patch (reevaluate) and instantiated per list row (template_instantiate_with);
• evaluator: the Evaluator trait the bindings go through, implemented by ExprEvaluator over the expr crate and used by default;
• fixtures: the test documents, exported for hosts' tests.

The node fence is parsed by strict and never executed. A binding may read $model anywhere and $item inside a list template; calls, assignments, statements and shell or Bus forms are refused at compile time with binding-policy.

Window declarations accept kind:"edge", kind:"dialog" and kind:"toast". Toasts are pointer-only overlays in compd, with optional w, h, title and chrome (false by default). The host clamps their geometry and manages visibility through its toast verbs.

Test: cargo test -p scene.

The source is libs/scene.