Add FxNode render graph playground

Add persistent render graph loadouts, grouped node authoring, code-appending apply behavior, explicit playground lighting, and resilient worker startup.

Amp-Thread-ID: https://ampcode.com/threads/T-01a033d4-0e44-708e-af0e-6166283416ff
Co-authored-by: Heaust Azure <heaust.azure@gmail.com>

server/web/assets/gltf.js

@@ -1,6 +1,7 @@
 import {
   AmbientLight,
   ArcRotateCamera,
+  PointLight,
   Scene,
   importGltf,
 } from "@yawn/handles";
@@ -223,24 +224,47 @@ async function openFile(file) {
     scene = new Scene(canvas, {
       arenaBytes: 384 * 1024 * 1024,
       hdr: true,
+      clearColor: [0.025, 0.035, 0.045, 1],
     });
     await scene.ready;
-    scene.array("sceneAccent").row(0).set([1, 1, 1, 1]);
 
     const meshes = await importGltf(scene, url);
     if (!meshes.length)
       throw new Error("The file does not contain any triangle meshes.");
 
     const bounds = findBounds(scene, meshes);
-    const light = new AmbientLight(scene, {
-      color: [1, 0.94, 0.86],
-      intensity: 0.28,
-    });
+    const radius = Math.max(bounds.radius, 0.001);
+    const lights = [
+      new AmbientLight(scene, {
+        color: [0.82, 0.9, 1],
+        intensity: 0.22,
+      }),
+      new PointLight(scene, {
+        position: [
+          bounds.center[0] + radius * 2.4,
+          bounds.center[1] + radius * 3.1,
+          bounds.center[2] + radius * 2.2,
+        ],
+        color: [1, 0.78, 0.56],
+        intensity: 300,
+        range: radius * 8,
+      }),
+      new PointLight(scene, {
+        position: [
+          bounds.center[0] - radius * 2.1,
+          bounds.center[1] + radius * 0.8,
+          bounds.center[2] - radius * 1.8,
+        ],
+        color: [0.45, 0.72, 1],
+        intensity: 120,
+        range: radius * 7,
+      }),
+    ];
     const camera = new ArcRotateCamera(
       scene,
       cameraOptions(scene, meshes, canvas, bounds),
     );
-    await Promise.all([light.ready, camera.ready]);
+    await Promise.all([...lights.map((light) => light.ready), camera.ready]);
 
     elements.renderValue.textContent = "— ms";
     elements.renderTime.hidden = false;
@@ -251,10 +275,7 @@ async function openFile(file) {
     if (!profiling)
       elements.renderTime.title =
         "GPU timestamp queries are not supported by this adapter.";
-    else {
-      elements.renderTime.removeAttribute("title");
-      scene.array("sceneAccent").row(0)[3] = 1;
-    }
+    else elements.renderTime.removeAttribute("title");
 
     activeViewer = {
       camera,