* Add the appearance model types and attribute constants
* Dual-write the appearance attribute alongside the fill/stroke pair in all paint-writing nodes
* Read paint from the appearance attribute in the renderer, analysis, metadata, and editor, cascading from ancestors
* Retire the fill/stroke attribute pair and the Vector stroke field in favor of the appearance attribute
* Replace the Stroke node's paint order input with the relative chain order of the Fill and Stroke nodes
* Code review fixes
* Re-save demo art
* Stamp coverages in place and fuse the renderer's per-item appearance reads into single walks
* Treat an empty appearance as the undeclared state so padded rows inherit instead of blocking the cascade
* Update demo art
* Treat padded appearance rows as undeclared in the boolean flatten's group recursion