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/ui/Theme.ts

@@ -55,6 +55,7 @@ export const Theme = {
     categoryVariable: 0xb8860b,
     categoryAction: 0x2f6fd6,
     categoryState: 0x8e5ad6,
+    categoryShader: 0x1f8f8f,
     portExec: 0xffffff,
     portNumber: 0x6fcf97,
     portBoolean: 0xe57373,
@@ -62,6 +63,7 @@ export const Theme = {
     portObject: 0x56ccf2,
     portList: 0xf2a75c,
     portStruct: 0xd4c25a,
+    portVec3: 0xff9ad5,
     portAny: 0xbdbdbd,
     /** Ring around the port a running edge drag would connect to. */
     portTarget: 0xffffff,