ci: test Node 20.x, 22.x, and 24.x; drop Node 18.x

Integration tests previously ran on Node 18.x and 20.x. Node 18 reached
end-of-life; CI now covers current LTS (20, 22) and Node 24.x.

Made-with: Cursor

Author: thomasrockhu-codecov

.github/workflows/ci.yml

@@ -278,7 +278,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node-version: ["18.x", "20.x"]
+        node-version: ["20.x", "22.x", "24.x"]
     steps:
       - name: Checkout
         uses: actions/checkout@v4