ci: test Node 24.10.0 only in test matrix

Reduces test matrix from 6 jobs (3 Node versions × 2 OS) to 2 jobs (1 Node × 2 OS).
Lint, build, type-check, and isolated tests remain on Node 22.

Author: jdalton

.github/workflows/ci.yml

@@ -79,7 +79,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node: [20, 22, 24]
+        node: ['24.10.0']
         os: [ubuntu-latest, windows-latest]
     steps:
       - name: Checkout code