Potential fix for code scanning alert no. 5: Workflow does not contain permissions

[lcn2]

Potential fix for https://github.com/lcn2/calc/security/code-scanning/5

In general, the problem is fixed by explicitly declaring a permissions block that limits the GITHUB_TOKEN to the minimum needed. Since this workflow only checks out code and runs local build commands, it does not need write access to repository contents or other scopes, so contents: read at the workflow or job level is sufficient.

The best fix without changing existing functionality is to add a top‑level permissions section (aligned with name and on) that sets contents: read. This applies to all jobs in the workflow and matches the CodeQL suggestion for a minimal starting point. No existing steps need to change, and no extra permissions (like pull-requests: write) are required based on the shown snippet.

Concretely, in .github/workflows/test.yml, between the name: C CI line and the on: block, insert:

permissions:
  contents: read

No imports, methods, or other code constructs are needed since this is a YAML configuration change only.

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