Add explicit permissions block to workflow

Limit GITHUB_TOKEN to read-only access for security best practices.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: jocelynlin-wd

.github/workflows/proprietary-path-guard.yml

@@ -24,6 +24,9 @@ on:
         required: false
         default: 'Testing'
 
+permissions:
+  contents: read
+
 jobs:
   check-proprietary-paths:
     name: Check for Proprietary Paths