fix: Correctly return list length in HandleLLengthCommand

The previous implementation of `HandleLLengthCommand` was not correctly returning the list length. It was using `ListStoreWithReadLock` in a way that didn't capture the return value.

This commit fixes this issue by:

- Modifying `ListOperations.cs` to use the generic `ListStoreWithReadLock` method correctly, ensuring that the length of the list is returned.
- Updating the XML documentation in both `artifacts/native/Firefly.xml` and `artifacts/exe/Firefly.xml` to accurately reflect that `HandleLLengthCommand` returns the length of the list.

artifacts/exe/Firefly.xml

@@ -227,6 +227,13 @@
             <param name="args">Command arguments containing the key</param>
             <returns>The popped value or nil if the list is empty</returns>
         </member>
+        <member name="M:Firefly.Firefly.HandleLLengthCommand(System.String)">
+            <summary>
+            Handles the LLEN command which returns the length of a list.
+            </summary>
+            <param name="args">Command arguments containing the key</param>
+            <returns>The length of the list or 0 if the key does not exist</returns>
+        </member>
         <member name="M:Firefly.Firefly.HandleLRangeCommand(System.String)">
             <summary>
             Handles the LRANGE command which returns a range of elements from a list.

artifacts/native/Firefly.xml

@@ -227,6 +227,13 @@
             <param name="args">Command arguments containing the key</param>
             <returns>The popped value or nil if the list is empty</returns>
         </member>
+        <member name="M:Firefly.Firefly.HandleLLengthCommand(System.String)">
+            <summary>
+            Handles the LLEN command which returns the length of a list.
+            </summary>
+            <param name="args">Command arguments containing the key</param>
+            <returns>The length of the list or 0 if the key does not exist</returns>
+        </member>
         <member name="M:Firefly.Firefly.HandleLRangeCommand(System.String)">
             <summary>
             Handles the LRANGE command which returns a range of elements from a list.

src/ListOperations.cs

@@ -165,13 +165,9 @@ namespace Firefly
             }
 
             string key = args.Trim();
-            int length = 0;
+            
-
+            // Change to use the generic method correctly by returning the length
-            // Use helper function to safely read the list with read lock
+            int length = ListStoreWithReadLock(key, list => list.Count);
-            ListStoreWithReadLock(key, list =>
-            {
-                length = list.Count;
-            });
 
             return Encoding.UTF8.GetBytes($":{length}\r\n");
         }