chore: drop Node.js 18 from CI build matrix

Remove Node.js 18.x from the build/test matrix, keeping only
Node.js 20.x and 22.x. Node 18 reached end-of-life on 2025-04-30.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: ramsessanchez

.github/workflows/build.yml

@@ -21,7 +21,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node-version: [18.x, 20.x, 22.x]
+        node-version: [20.x, 22.x]
         # Single version should work for compilation testing
 
     steps: