Fix grading: clamp scores to (0,1) exclusive

server/tasks.py

@@ -404,5 +404,6 @@ _GRADERS: dict[str, Callable[[str], float]] = {
 def grade_answer(task_id: str, answer: str) -> float:
     grader = _GRADERS.get(task_id)
     if grader is None:
-        return 0.0
-    return grader(answer)
+        return 0.05
+    raw = grader(answer)
+    return max(0.05, min(0.95, raw))