osk: add first osk test

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 67.55%. Comparing base (1795682) to head (c137f99). Report is 3 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #109 +/- ## ========================================== + Coverage 67.19% 67.55% +0.35% ========================================== Files 16 16 Lines 817 826 +9 Branches 114 114 ========================================== + Hits 549 558 +9 Misses 244 244 Partials 24 24 ```

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[Saviq]

It should have used variants/noble/01_pluma.png.

Hmm! But your OSK is not noble o.O

What does python3 -c 'from mir_ci import VARIANT; print(VARIANT)' say?

You can override the variant with MIR_CI_VARIANT=, FWIW.