ci(precommit): 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/precommit.yaml

@@ -7,6 +7,9 @@ on:
       - main
   pull_request:
 
+permissions:
+  contents: read
+
 jobs:
   test:
     name: Run pre-commit.ci