Add interactive tutorial playgrounds

Embed editable split-view examples throughout the guide, restore the full LFS-backed Sponza demo, batch glTF hydration, honor hierarchical transforms, and report transformed BVH picks with a live FPS counter.

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

.agents/setup

@@ -10,5 +10,11 @@ rustup toolchain install "$toolchain" --profile minimal --component rust-src,rus
 if ! command -v wasm-pack >/dev/null; then
     cargo install wasm-pack --version 0.15.0 --locked
 fi
+if ! command -v git-lfs >/dev/null; then
+    sudo apt-get update -qq
+    sudo apt-get install -y git-lfs
+fi
+git lfs install --local
+git lfs pull --include="docs/public/models/sponza.glb"
 npm ci
 amp orb services ensure