test: add test for per-attack image directories and improve error handling

- Add test_generate_test_cases.py to verify each attack uses its own image directory
- Improve error messages in unified_registry for failed imports with more context
- Add null checks in generate_test_cases.py for attack initialization failures
- Reduce excessive max_tokens in judge_utils from 130000 to 10000 for efficiency
- Add missing ThreadPoolExecutor import in qr/attack.py
- Fix missing newline in pyproject.toml

pyproject.toml

@@ -96,4 +96,4 @@ explicit = true
 
 [tool.uv.sources]
 torch = { index = "pytorch-cu118" }
-torchvision = { index = "pytorch-cu118" }
+torchvision = { index = "pytorch-cu118" }