chore(actions): update Node.js runtime from node20 to node24

Node.js 20 reaches EOL in April 2026 and GitHub Actions is deprecating
node20 runners. GitHub is skipping node22 and moving directly to node24.
All action.yml files updated to use node24 runtime.

Closes #87

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

install/action.yml

@@ -17,5 +17,5 @@ inputs:
     default: '0'
     required: false
 runs:
-  using: 'node20'
+  using: 'node24'
   main: 'index.js'