fix: update stale workflow permissions for reusable workflow compatibility

[Copilot]

The stale workflow was failing due to insufficient permissions for the reusable workflow at cpp-linter/.github/.github/workflows/stale.yml@main.

Error:

Invalid workflow file: .github/workflows/stale.yml#L9
The workflow is not valid. .github/workflows/stale.yml (Line: 9, Col: 3): Error calling workflow 'cpp-linter/.github/.github/workflows/stale.yml@main'. The nested job 'stale' is requesting 'contents: read, pull-requests: write', but is only allowed 'contents: none, pull-requests: none'.

Root Cause:
The calling workflow only provided issues: write permission at the workflow level, but the reusable workflow's job requires contents: read and pull-requests: write permissions that weren't being inherited.

Solution:
Following security best practices with the principle of least privilege:

1. Set workflow-level permissions to empty (permissions: {})
2. Add job-level permissions specifically for the stale job with required access:
   • contents: read - Required by the reusable workflow
   • issues: write - Maintained existing functionality
   • pull-requests: write - Added missing permission that was causing the failure

This change ensures the reusable workflow has the necessary permissions while maintaining security through job-level permission scoping.

Fixes #128.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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