Shader assets: graph-built shaders, the Shader tab and sprite rows from the graph (#62)

A shader is an asset carrying a node graph (Texture color, Output, Property,
Color, Add/Subtract/Multiply/Divide, Mix, Luminance) that compiles to the GLSL
fragment of a Pixi filter. The Shader tab reuses the Behavior canvas; a sprite
wears a shader through its Shader picker, and the rows below it are the
graph's Property nodes. Property schema, resolution and deviation take the
project because a sprite's rows now live in another asset. The built-in
registry of the prototype is gone; "Adjust colors" ships as a graph in the
fixture and the three example games.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/core/graph/NodeRegistry.ts

@@ -16,8 +16,11 @@ export interface PortDef {
   field?: PropertyDef;
 }
 
-/** `state` is the one category no behavior graph offers: its nodes are the states of a state machine. */
-export type NodeCategory = 'event' | 'flow' | 'data' | 'variable' | 'action' | 'state';
+/**
+ * `state` and `shader` are the categories no behavior graph offers: their nodes are the states of
+ * a state machine and the GLSL of a shader asset.
+ */
+export type NodeCategory = 'event' | 'flow' | 'data' | 'variable' | 'action' | 'state' | 'shader';
 
 /**
  * How a loop node asks for one of its exec outputs to be run repeatedly: `port` carries the body,
@@ -134,13 +137,15 @@ export function hasExecInput(def: NodeDef): boolean {
 
 /**
  * Data inputs that may carry an inline value while unconnected. An object is a live handle and a
- * struct is assembled from its parts, so neither has a value that could be typed on one line.
+ * struct is assembled from its parts, so neither has a value that could be typed on one line; a
+ * shader colour has one only where the node gives it a colour field.
  */
 export function inlineInputs(def: NodeDef): PortDef[] {
   return def.inputs.filter(isInlinePort);
 }
 
 function isInlinePort(port: PortDef): boolean {
+  if (port.type === 'vec3') return port.field !== undefined;
   return port.type !== 'exec' && port.type !== 'object' && port.type !== 'struct';
 }