Fix Node 18 CI docs step by including optional dependencies

The "Check docs" step ran `npm ci` without `--include=optional`,
which removed @huggingface/transformers. Typedoc then failed because
it couldn't resolve the type imports from that package.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/nodejs.yml

@@ -126,7 +126,7 @@ jobs:
         # We run this as part of the job because the binary needs to be built
         # first to export the types of the native code.
         set -e
-        npm ci
+        npm ci --include=optional
         npm run docs
         if ! git diff --exit-code -- ../ ':(exclude)Cargo.lock'; then
           echo "Docs need to be updated"