build(emsdk): update to latest version and fix unused import warning

Updates CI/CD emsdk from pinned 3.1.43 to latest (4.0.22), resolving a version
mismatch between local dev (which used latest) and production builds. This
discrepancy likely caused production-only ErrnoError bugs that were impossible
to reproduce locally.

.github/workflows/deploy.yaml

@@ -27,7 +27,7 @@ jobs:
       - name: Setup Emscripten SDK
         uses: pyodide/setup-emsdk@v15
         with:
-          version: 3.1.43
+          version: latest
           actions-cache-folder: "emsdk-cache-b"
 
       - name: Setup Rust (WASM32 Emscripten)