fix(npm): use the Huawei npm mirror

Only Huawei works with prefetch-npm-deps: npmmirror 404s on its doubled
slash, and Tencent answers 567 to its concurrent fetches (WA-049).

Assisted-by: Claude Code (claude-opus-5-5)

outputs/default.nix

@@ -14,8 +14,10 @@ let
   # fetchNpmDeps (package-lock tarballs and registry packuments).
   nixpkgsConfig = {
     allowUnfree = true;
+    # Only Huawei works here: npmmirror 404s on prefetch-npm-deps' doubled
+    # slash, and Tencent answers 567 to its concurrent fetches (WA-049).
     npmRegistryOverrides = {
-      "registry.npmjs.org" = "https://registry.npmmirror.com";
+      "registry.npmjs.org" = "https://mirrors.huaweicloud.com/repository/npm";
     };
     rewriteURL =
       url: