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/PostProcesses/ColorGrading.ts

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+import { PostProcess } from "./PostProcess";
+import type { Scene } from "../Scene";
+
+export type ToneMap = "aces" | "reinhard" | "linear";
+export class ColorGrading extends PostProcess {
+  constructor(scene: Scene, options: { amount?: number; toneMap?: ToneMap; enabled?: boolean } = {}) {
+    super(scene, "colorGrading", options);
+  }
+}

addons/handles/src/PostProcesses/DynamicExposure.ts

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+import { PostProcess } from "./PostProcess";
+import type { Scene } from "../Scene";
+
+export class DynamicExposure extends PostProcess {
+  constructor(scene: Scene, options: { exposure?: number; enabled?: boolean } = {}) { super(scene, "dynamicExposure", options); }
+}

addons/handles/src/PostProcesses/Edges.ts

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+import { PostProcess } from "./PostProcess";
+import type { Scene } from "../Scene";
+
+export class Edges extends PostProcess {
+  constructor(scene: Scene, options: { amount?: number; enabled?: boolean } = {}) { super(scene, "edges", options); }
+}

addons/handles/src/PostProcesses/FXAA.ts

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+import { PostProcess } from "./PostProcess";
+import type { Scene } from "../Scene";
+
+export class FXAA extends PostProcess {
+  constructor(scene: Scene, options: { enabled?: boolean } = {}) { super(scene, "fxaa", options); }
+}

addons/handles/src/PostProcesses/PostProcess.ts

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+import type { Scene } from "../Scene";
+
+let nextPostProcess = 1;
+
+/** Shared graph-membership behavior for the small post-process handles. */
+export class PostProcess {
+  readonly scene: Scene;
+  readonly id: string;
+  readonly kind: string;
+  options: Record<string, unknown>;
+  enabled: boolean;
+  ready: Promise<void>;
+
+  protected constructor(scene: Scene, kind: string, options: Record<string, unknown> = {}) {
+    this.scene = scene;
+    this.kind = kind;
+    this.id = `${kind}-${nextPostProcess++}`;
+    this.enabled = options.enabled !== false;
+    const { enabled: _, ...effectOptions } = options;
+    this.options = effectOptions;
+    this.ready = scene.setPostProcess(this, this.enabled);
+  }
+
+  setEnabled(enabled: boolean) {
+    this.enabled = enabled;
+    this.ready = this.scene.setPostProcess(this, enabled);
+    return this.ready;
+  }
+
+  update(options: Record<string, unknown>) {
+    this.options = { ...this.options, ...options };
+    this.ready = this.scene.setPostProcess(this, this.enabled);
+    return this.ready;
+  }
+
+  dispose() { return this.setEnabled(false); }
+}

addons/handles/src/PostProcesses/SSAO.ts

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+import { PostProcess } from "./PostProcess";
+import type { Scene } from "../Scene";
+
+export class SSAO extends PostProcess {
+  constructor(scene: Scene, options: { amount?: number; enabled?: boolean } = {}) { super(scene, "ssao", options); }
+}

addons/handles/src/PostProcesses/Silhouette.ts

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+import { PostProcess } from "./PostProcess";
+import type { Scene } from "../Scene";
+
+export class Silhouette extends PostProcess {
+  constructor(scene: Scene, options: { amount?: number; enabled?: boolean } = {}) { super(scene, "silhouette", options); }
+}