Adopt the cascading "appearance" attribute in place of Vector::stroke and the "fill"/"paint" attributes (#4433)

* 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

node-graph/graph-craft/src/document/value.rs

@@ -550,7 +550,6 @@ tagged_value! {
 	#[serde(alias = "LineJoin")]
 	StrokeJoin(vector::style::StrokeJoin),
 	StrokeAlign(vector::style::StrokeAlign),
-	PaintOrder(vector::style::PaintOrder),
 	#[serde(alias = "GradientType")] // TODO: Eventually remove this document upgrade code
 	GradientForm(vector::style::GradientForm),
 	#[serde(alias = "GradientSpreadMethod")] // TODO: Eventually remove this document upgrade code
@@ -564,8 +563,9 @@ tagged_value! {
 	TextAlign(text_nodes::TextAlign),
 	ScaleType(core_types::transform::ScaleType),
 	// Legacy
+	PaintOrder(vector::style::PaintOrder), // TODO: Eventually remove this document upgrade code
 	#[serde(alias = "Fill")]
-	LegacyFill(graphic_types::migrations::legacy::LegacyFill),
+	LegacyFill(graphic_types::migrations::legacy::LegacyFill), // TODO: Eventually remove this document upgrade code
 }
 
 impl TaggedValue {