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>

docs/guide/post-processing.md

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+# Post processing
+
+Post-process handles insert or remove graph passes. Intermediate HDR textures are transient and compatible non-overlapping lifetimes alias the same physical allocation.
+
+```ts
+const ssao = new SSAO(scene, { amount: 0.8 });
+const exposure = new DynamicExposure(scene, { exposure: 1.1 });
+const grade = new ColorGrading(scene, { toneMap: "aces", amount: 1.0 });
+const fxaa = new FXAA(scene);
+
+await Promise.all([ssao.ready, exposure.ready, grade.ready, fxaa.ready]);
+```
+
+<Playground example="post" />
+
+Every effect is optional:
+
+```ts
+await ssao.setEnabled(false);
+await grade.update({ toneMap: "reinhard" });
+await fxaa.dispose();
+```
+
+Also available:
+
+```ts
+const outline = new Silhouette(scene, { amount: 1 });
+const edgeImage = new Edges(scene, { amount: 2, enabled: false });
+await edgeImage.setEnabled(true);
+```
+
+The final present pass tone-maps HDR to the canvas. `ColorGrading` supports `aces`, `reinhard`, and `linear` tone maps.
+
+<script setup>
+import Playground from "../.vitepress/Playground.vue";
+</script>