fix: creating a room failed with a blank "Failed to copy room"

The 2023 client sends rooms/{id}/clone through the same RecNet rooms
helper as "save room" and "restore subroom save", which reads the
{success, value, error} envelope. The clone handler answered with the
bare room details, so the client found no success flag and rejected the
reply with an empty error, even though the room had been created.

Clone now returns the envelope with the full room details in value, and
refusals (unknown source, cloning not allowed) are a 200 with
success=false and a message instead of a bodyless 404/403.

DorkNet.Server/Controllers/API/Rooms/V2/RoomsModerationController.cs

@@ -1375,13 +1375,13 @@ public class RoomsModerationController(
     {
         var newName = await ReadCloneNameAsync();
         var source = await db.Rooms.FirstOrDefaultAsync(r => r.Id == roomId);
-        if (source is null) return NotFound();
+        if (source is null) return CloneResult(null, "That room doesn't exist.");
         // RRO/AG rooms are first-party templates meant to be cloned — the
         // room-creation "base room" picker starts a new build by cloning one
         // (RecCenter, MakerRoom, …). Their seed rows have CloningAllowed=false,
-        // so without the IsAGRoom exception every base-room create 403s.
+        // so without the IsAGRoom exception every base-room create is refused.
         if (!source.CloningAllowed && !source.IsAGRoom && source.CreatorPlayerId != Me)
-            return Forbid();
+            return CloneResult(null, "You can't clone this room!");
 
         if (string.IsNullOrWhiteSpace(newName))
             newName = $"{source.Name}Copy";
@@ -1517,17 +1517,22 @@ public class RoomsModerationController(
 
         await GiveCloneItsOwnBlobsAsync(clone, sourceScenes, clonedScenes, Me);
 
-        // The 2023 client's clone (RecNet.Runtime NLDBPDCNNCF.GDHIIAHCBMN)
-        // deserializes the response as the FULL room-details object
-        // (FGCPNAACHIK — the same type get-by-id / rename return on the
-        // roomserver host), NOT the slim list-room shape. This is the
-        // roomserver-family path (rooms/{id}/clone), so use
-        // BuildRoomServerDetails — the exact shape GET rooms/{id} returns for
-        // the 2023 client. Returning ToWireRoom (or the wrong details variant)
-        // made the strict reader fail → "Failed to copy room: Failed to clone
-        // room".
-        return Ok(RoomsController.BuildRoomServerDetails(clone, clonedScenes));
+        // The value is the FULL room-details object (FGCPNAACHIK), the exact
+        // shape GET rooms/{id} returns for the 2023 client — not the slim
+        // list-room shape, which made the strict reader fail.
+        return CloneResult(RoomsController.BuildRoomServerDetails(clone, clonedScenes));
     }
+    /// <summary>Reply for <c>rooms/{id}/clone</c>. The 2023 client sends the
+    /// clone through the same RecNet rooms helper as "save room" and "restore
+    /// subroom save" (NLDBPDCNNCF.BDBHCEGKGDC with an op name), which reads the
+    /// legacy <c>{success, value, error}</c> envelope. A bare room-details body
+    /// has no <c>success</c>, so the client rejects it with an empty error:
+    /// "Failed to copy room: Exception of type 'CEMNLBKJABA' was thrown", even
+    /// though the room was created. Refusals are 200 with success=false and a
+    /// message the client shows.</summary>
+    private OkObjectResult CloneResult(object? room, string error = "") =>
+        Ok(new { success = error.Length == 0, value = room, error });
+
     /// <summary>Give a freshly-cloned room its OWN copy of the source's save
     /// data instead of pointing its scenes at the source's blob.
     ///