fix(ci): grant issues:write to verify-links workflow

Weekly scheduled run was failing with 'Resource not accessible by
integration' when trying to open a maintenance issue. Default
GITHUB_TOKEN is read-only for contents and has no access to issues
under restrictive repo defaults.

.github/workflows/verify-links.yml

@@ -6,6 +6,10 @@ on:
     - cron: '0 3 * * 1'
   workflow_dispatch:  # Allow manual triggering
 
+permissions:
+  contents: read
+  issues: write
+
 jobs:
   verify:
     runs-on: ubuntu-latest