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 from Actions run:

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 granted issues: write at the workflow level, but the reusable workflow's job requires additional permissions (contents: read and pull-requests: write) that were not available.

Solution:
Following GitHub Actions security best practices with job-level permissions (principle of least privilege):

1. Set workflow-level permissions to permissions: {} (empty)
2. Grant specific permissions only to the job that needs them:
   • contents: read
   • issues: write
   • pull-requests: write

This ensures the reusable workflow receives all required permissions while maintaining minimal privilege scope.

Before:

permissions:
  issues: write

jobs:
  stale:
    uses: cpp-linter/.github/.github/workflows/stale.yml@main

After:

permissions: {}

jobs:
  stale:
    permissions:
      contents: read
      issues: write
      pull-requests: write
    uses: cpp-linter/.github/.github/workflows/stale.yml@main

Fixes #333.

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[shenxianpeng]

duplicate with #334

[2bndy5]

I'm getting confused which repo is which. All the related issues and PRs look the same.