Allow non testcase folders under testcases

**Steps**
Create an empty folder under "testcases"
run the summarize report

**Describe the bug**

Summarizing evaluation results in user-actions
Found 3 testcases: ['gemini2flash', 'gemini2flashlight', 'frames']
An unexpected error occurred: Eval results file not found at user-actions/testcases/frames/eval_results.jsonl

**Expected behavior**
the empty folder should be ignored, with a warning

