Fix Phase 2: Add missing required metadata to prevent Pydantic drops

openenv.yaml

@@ -8,8 +8,17 @@ models:
 env: "env:BlockchainEnv"
 tasks:
   - id: "easy_minting"
+    name: "Easy Minting"
+    description: "Successfully mint valid certificates."
+    difficulty: "easy"
     grader: "graders:grade_easy"
   - id: "medium_gas_management"
+    name: "Medium Gas Management"
+    description: "Manage gas appropriately across batches."
+    difficulty: "medium"
     grader: "graders:grade_medium"
   - id: "hard_perfectionist"
+    name: "Hard Perfectionist"
+    description: "Complete full trajectories without errors."
+    difficulty: "hard"
     grader: "graders:grade_hard"