ci(build-test): cap GITHUB_TOKEN to contents: read

Workflow runs checks only; no GitHub API writes. Post-CVE-2025-30066 hardening pattern.

Signed-off-by: Arpit Jain <arpitjain099@gmail.com>

Author: arpitjain099

.github/workflows/build-test.yml

@@ -15,6 +15,9 @@ on:
       - genMatrix.js
       - ".github/workflows/build-test.yml"
 
+permissions:
+  contents: read
+
 jobs:
   gen-matrix:
     name: generate-matrix