fix(ci): initialize git submodules in coverage workflow

- Add submodules: true to checkout step for consistency with other workflows
- Ensures all submodules are available during coverage builds

Author: ahojukka5

.github/workflows/coverage.yml

@@ -23,6 +23,8 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
+        with:
+          submodules: true
 
       - name: Install dependencies
         run: |