ci: run on Node 20/22 (vitest 4 toolchain needs Node 20+)

The vitest 4 / rolldown test toolchain imports `styleText` from
node:util, which only exists on Node 20+, so the test step fails on
Node 18. The published CLI bundle still targets Node 18; CI builds and
tests on the versions the dev toolchain supports.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: meganfoster-dotcom

.github/workflows/ci.yml

@@ -18,7 +18,10 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node: ["18", "20", "22"]
+        # The dev/test toolchain (vitest 4 via rolldown) requires Node 20+
+        # (it imports `styleText` from node:util, added in Node 20). The published
+        # CLI bundle still targets Node 18, but CI builds and tests on 20/22.
+        node: ["20", "22"]
     steps:
       - name: Checkout
         uses: actions/checkout@v4