feat: Add digit-based number range generation for chain sum tasks

tests/test_chain_sum.py

@@ -49,3 +49,27 @@ def test_chain_sum_items():
         # Verify the answer matches the expression
         answer = eval(expression)  # Safe here as we control the expression
         assert str(answer) == item["answer"]
+
+
+def test_chain_sum_number_ranges():
+    """Test that generated numbers respect digit constraints"""
+    config = ChainSumConfig(
+        min_terms=2,
+        max_terms=2,  # Fix to 2 terms for easier testing
+        min_digits=3,  # Should generate numbers >= 100
+        max_digits=3,  # Should generate numbers <= 999
+        size=50,
+        seed=42
+    )
+    dataset = ChainSum(config)
+    
+    for i in range(len(dataset)):
+        item = dataset[i]
+        expression = item["metadata"]["expression"]
+        
+        # Extract numbers from expression
+        numbers = [int(n) for n in expression.split() if n.isdigit()]
+        
+        # Verify each number is in the correct range
+        for num in numbers:
+            assert 100 <= num <= 999, f"Number {num} outside valid range for 3 digits"