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/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "@yawn/handles",
+  "version": "0.1.0",
+  "description": "Conventional scene handles over Yawn's worker and shared render data",
+  "type": "module",
+  "exports": "./src/index.ts",
+  "dependencies": {
+    "@yawn/core": "0.1.0"
+  }
+}