* feat: write variable-bound properties as tokens in exported code
HTML and Tailwind JSX export reference the design tokens a layer is bound to, var(--color-primary) or bg-primary, instead of baking in their values. A binding becomes a reference only where the stylesheet resolves it as the canvas draws it: the layer still draws the value, the token's unit fits the property, and an attribute such as data-theme="dark" can put the element in the layer's mode. Standalone HTML includes the stylesheet for the tokens it uses, compiled into Tailwind's @theme for Tailwind pages.
* refactor: share the collection variable list and tighten token helpers
Read every variable in collection order through one collectionVariables helper built on es-toolkit's compact, used by the stylesheet and the token references, and map padding sides and color channels instead of repeating them.
* refactor(dom-css): group sources into import, export, and runtime
dom-css kept both conversion directions in one flat folder: HTML and CSS
import next to SceneGraph export, a JSX runtime next to the Tailwind JSX
printer, and CSS parsing and formatting in one file.
Sources now live in `import/`, `export/`, and `runtime/`, with the CSS
value helpers split by direction and `export/index.ts` as the `./export`
entry. Tests mirror the new folders. Public entry points are unchanged.
* docs(dom-css): add a package guide for the import, export, and runtime layout
dom-css had no AGENTS.md. The guide records the source layout, the
scene-graph-only dependency, the browser-safe `./export` entry, printed
code generation, and Base64 validation for imported documents, and the
root map links to it.
