Replace addons with conventional handles

Provide the single-loadout Scene API, SAB-backed meshes, cameras, materials, lights, workers, post effects, and tutorial playgrounds. Batch matching row growth so active GPU loadouts refresh once.

Amp-Thread-ID: https://ampcode.com/threads/T-01a01380-b478-77d0-84a0-102880a5c5ae
Co-authored-by: Heaust Azure <heaust.azure@gmail.com>

addons/handles/src/lights/RectAreaLight.ts

@@ -0,0 +1,39 @@
+import { Node, type NodeOptions } from "../Node";
+import type { Scene } from "../Scene";
+
+export type RectAreaLightOptions = NodeOptions & {
+  color?: ArrayLike<number>;
+  intensity?: number;
+  width?: number;
+  height?: number;
+};
+
+/** Rectangular emitter data for the default clustered forward graph's LTC path. */
+export class RectAreaLight extends Node {
+  readonly technique = "ltc";
+
+  constructor(scene: Scene, options: RectAreaLightOptions = {}) {
+    super(scene, options);
+    const nodeReady = this.ready;
+    this.ready = nodeReady.then(async () => {
+      const array = await scene.ensureRows("rectAreaLights", this.id + 1, 48, "f32");
+      array.row(this.id).set([
+        ...Array.from(options.color ?? [1, 1, 1]), options.intensity ?? 1,
+        options.width ?? 1, options.height ?? 1, 1, 0,
+      ]);
+      return this;
+    });
+  }
+
+  get width() { return this.scene.array("rectAreaLights").row(this.id)[4]; }
+  set width(value: number) { this.scene.array("rectAreaLights").row(this.id)[4] = value; }
+  get height() { return this.scene.array("rectAreaLights").row(this.id)[5]; }
+  set height(value: number) { this.scene.array("rectAreaLights").row(this.id)[5] = value; }
+
+  override async dispose() {
+    await this.ready;
+    if (this.disposed) return;
+    this.scene.array("rectAreaLights").row(this.id).fill(0);
+    await super.dispose();
+  }
+}