fix: transform image demo crash by pinning @emnapi to 1.8.1

[DaanyaalSobani]

Summary

Fixes the homepage's "Transform Image App" demo, which throws TypeError: Cannot read properties of undefined (reading 'whenLoaded') in Chrome on click.

Refs napi-rs/napi-rs#3262

Root cause

@napi-rs/image-wasm32-wasi's prebuilt .wasm is linked against emnapi 1.8.x, which uses an internal worker-pool to track threads. But @napi-rs/wasm-runtime resolves @emnapi/core to ^1.7.1, which in practice installs 1.10.0 — and from 1.9.0 onward, emnapi switched to delegating to pthread_create and stopped maintaining a separate pool. The JS runtime then reads a tid from a memory location the prebuilt wasm never populates, so PThread.pthreads[tid] is undefined when initWorkers tries to read .whenLoaded on it.

This is the same mismatch reported and explained in toyobayashi/emnapi#202.

Changes

• package.json: pin @emnapi/core and @emnapi/runtime to 1.8.1 via resolutions so the JS runtime matches what the prebuilt .wasm was linked against.
• next.config.js: add COOP/COEP at the document level and Cross-Origin-Resource-Policy: same-origin on /_next/static/*. middleware.js already set COOP/COEP on HTML, but Next.js middleware doesn't run on /_next/static/*, so static worker chunks lacked CORP — required under Cross-Origin-Embedder-Policy: require-corp for SharedArrayBuffer-backed wasm threading.

Test plan

• yarn dev → open homepage → click Transform image to webp → completes successfully (previously threw)
• DevTools console: crossOriginIsolated === true
• All 5 image.wasm32-wasi.*.wasm requests return 200

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[DaanyaalSobani]

Recording.2026-04-30.185711.mp4

Video showing the button is working after applying the fix.