Fix: grader field must be plain string in openenv.yaml and GET /tasks

openenv.yaml

@@ -149,11 +149,7 @@ tasks:
       straightforward for a competent agent.
     dataset: tasks/easy/scenarios.json
     n_scenarios: 5
-    grader:
-      enabled: true
-      class: tasks.easy.grader.grade
-      fn: tasks.easy.grader.grade
-      score_range: [0.0, 1.0]
+    grader: tasks.easy.grader.grade
     weights: { decision: 0.50, evidence: 0.25, reasoning: 0.15, efficiency: 0.10 }
     ideal_max_steps: 8
     ground_truth_distribution: { allow: 1, flag: 1, remove: 3 }
@@ -166,11 +162,7 @@ tasks:
       and evidence weighing.
     dataset: tasks/medium/scenarios.json
     n_scenarios: 5
-    grader:
-      enabled: true
-      class: tasks.medium.grader.grade
-      fn: tasks.medium.grader.grade
-      score_range: [0.0, 1.0]
+    grader: tasks.medium.grader.grade
     weights: { decision: 0.35, evidence: 0.35, reasoning: 0.20, efficiency: 0.10 }
     ideal_max_steps: 12
     ground_truth_distribution: { allow: 1, flag: 4, remove: 0 }
@@ -183,11 +175,7 @@ tasks:
       tolerance for ambiguity.  All four scoring dimensions count equally.
     dataset: tasks/hard/scenarios.json
     n_scenarios: 5
-    grader:
-      enabled: true
-      class: tasks.hard.grader.grade
-      fn: tasks.hard.grader.grade
-      score_range: [0.0, 1.0]
+    grader: tasks.hard.grader.grade
     weights: { decision: 0.30, evidence: 0.30, reasoning: 0.30, efficiency: 0.10 }
     ideal_max_steps: 18
     ground_truth_distribution: { allow: 0, flag: 5, remove: 0 }

server.py

@@ -310,14 +310,9 @@ async def list_tasks():
                 ),
                 "n_scenarios": len(task),
                 "scenario_ids": [s["id"] for s in task.get_all_scenarios()],
-                "grader": {
-                    "enabled": True,
-                    "class": f"tasks.{difficulty}.grader.grade",
-                    "fn":    f"tasks.{difficulty}.grader.grade",
-                    "score_range": [0.0, 1.0],
-                },
-                "grader_fn":     f"tasks.{difficulty}.grader.grade",
-                "score_range":   [0.0, 1.0],
+                "grader":      f"tasks.{difficulty}.grader.grade",
+                "grader_fn":   f"tasks.{difficulty}.grader.grade",
+                "score_range": [0.0, 1.0],
                 "grader_weights": {
                     "decision":   grader.W_DECISION,
                     "evidence":   grader.W_EVIDENCE,