ci: add black --diff to show formatting issues

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: moffa90

.github/workflows/ci.yml

@@ -35,6 +35,7 @@ jobs:
     
     - name: Check formatting with black
       run: |
+        black --diff emc2305/ tests/ || true
         black --check emc2305/ tests/
     
     - name: Check import sorting with isort