webgl_batch_lod_bvh: blocked on an upstream packaging gap in @three.ez/batched-mesh-extensions

What

webgl_batch_lod_bvh is not ported (Phase 2). Two independent, stacked blockers, checked
directly against what's installed:

1. @three.ez/batched-mesh-extensions's WebGPU build is not importable. The installed
   package (0.0.12) genuinely ships a WebGPU build on disk (build/webgpu.js,
   src/index.webgpu.js, src/patch/ExtendBatchedMeshPrototype.webgpu.js all exist) — but
   package.json's exports field maps "." to build/webgl.js/.cjs only. There's no
   "webgpu" export condition and no subpath export, so Node/Vite's exports resolution
   refuses any path not listed there. A plain import '@three.ez/batched-mesh-extensions'
   always gets the WebGL build; reaching build/webgpu.js would need a private relative
   node_modules/... import into someone else's package layout, which isn't a real fix.
   Ledgered as UPSTREAM.md brief B51 — almost certainly a publishing oversight (the source
   clearly builds both targets), not an intentional WebGL-only package.
2. Two more dependencies aren't installed: @three.ez/simplify-geometry (generates the
   demo's 4 extra LOD levels from the base mesh) and meshoptimizer (the simplifier's
   backend). Adding them needs pnpm install, outside an agent's rules of engagement.

Also worth noting: the r185 original is itself WebGLRenderer-only despite the webgl_
prefix pattern holding — it explicitly imports the WebGL build from a CDN, i.e. even
upstream picks WebGL on purpose for this demo. A port would still be WebGPU-first per this
repo's charter, once unblocked.

Why it matters

Single-demo blocker, not site-wide — one example stays unported until the upstream
packaging gap closes. Filing so it isn't silently forgotten and so the next person doesn't
re-investigate from scratch.

Recommendation already on file

docs/REVIEW-QUEUE.md #15: (a) file an issue/PR upstream against
@three.ez/batched-mesh-extensions adding a "webgpu" export condition — cheap, and
unblocks this immediately once released; (b) in the meantime, do NOT work around it with a
relative deep import + declare module shim — that's exactly the kind of fragile,
non-portable hack AGENTS.md's "no dependency patches" rule exists to keep out. Wait for (a)
or skip the example. Not touched; no partial file on disk.

Pointer

docs/REVIEW-QUEUE.md §15 and docs/UPSTREAM.md brief B51.

Start with docs/REVIEW-QUEUE.md §15 and docs/UPSTREAM.md brief B51. Verify that the upstream package exposes a WebGPU export and that the missing dependencies are installed before attempting the port. Done means the upstream packaging gap is resolved and the webgl_batch_lod_bvh example is ported without a relative deep-import workaround.