Shader library: fingerprint without node positions, a drag no longer recompiles (#65)

shaderFingerprint(graph) covers node id/type/params/ports and edge endpoints only;
x/y, collapsed, folded and edge ids stay out. ShaderLibrary keys on it and counts
compiles (__gm.shaderCompiles()). Measured before: one compile per preview step of a
node drag (12 for a harness drag); after: 0, a param change exactly +1.

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

src/core/shader/compile.ts

@@ -47,6 +47,18 @@ export interface ShaderBuild {
  * becomes one local per output, in dependency order, and every Property a float uniform. The texel
  * arrives premultiplied, so the prelude unpremultiplies and the epilogue multiplies back.
  */
+/**
+ * What the fragment depends on and nothing else: node ids, types, params and declared ports, and
+ * which port feeds which. Positions, collapsing and folding are the editor's; they stay out so a
+ * moved node does not compile again (#65).
+ */
+export function shaderFingerprint(graph: Graph): string {
+  return JSON.stringify({
+    nodes: graph.nodes.map((n) => [n.id, n.type, n.params, n.ports ?? null]),
+    edges: graph.edges.map((e) => [e.from.node, e.from.port, e.to.node, e.to.port]),
+  });
+}
+
 export function compileShader(graph: Graph): ShaderBuild {
   const problems: Record<string, string> = {};
   const problem = (node: GraphNode, text: string) => {