fix: a cloned template carries its content instead of starting empty

Cloning a first-party template (RecCenter and friends) deliberately left the
new room with no blob, on the reasoning that its content is baked client
geometry and any blob is just a MakerPen overlay. That left the copy with
nothing to load.

The copy flow is what exposes it. IBEOONPEELF.GetRoomData / GetRoomMetadata
fetch "/room/{blob}" from the CDN as part of copying and throw a
BCPHBJHOIEM-family exception when that does not give them a usable room —
surfacing as the bare "Failed to copy room: Exception of type 'CEMNLBKJABA'"
with no message. For a name nothing is stored under, the CDN synthesises a
~1.8 KB stub: room_1583_dorknet_v8.dat served 1872 bytes where the source's
room_100_v1.dat is 10,930. The clone that DID work carried real content.

Since GiveCloneItsOwnBlobsAsync copies the bytes under the clone's own name,
the original worry — inheriting an overlay on a SHARED template — no longer
applies: nothing is shared either way. IsFirstPartyTemplate had no other
callers and is gone.

The existing assertion that a template clone must have NO blob encoded the
belief this replaces, so it now asserts the clone carries content. The
"doesn't share the source's object" half is covered by
RoomCloneShapeTests.Clone_does_not_reference_the_source_rooms_blob, which runs
with a real object store; this suite has none and deliberately falls back to
keeping the reference.

DorkNet.Server.Tests/RoomSave2023Tests.cs

@@ -198,8 +198,22 @@ public sealed class RoomSave2023Tests : IClassFixture<DorkNetServerFactory>
         var firstCloneId = await CloneAndAssertAsync(
             roomsClient, roomId, "FirstClone", pathPrefix: "/roomserver");
         Assert.NotEqual(roomId, firstCloneId);
-        await AssertBlobsAsync(firstCloneId, expectEmpty: true,
-            "first-party template blob must not be copied onto the clone");
+        // A clone of a first-party template used to be left with NO blob, on
+        // the reasoning that its content is baked client geometry. That left
+        // the copy with nothing to load: the CDN synthesises a ~1.8 KB stub for
+        // a name it has nothing stored under, and the client fetches exactly
+        // that through GetRoomData ("/room/{blob}") while copying, then rejects
+        // it. Clones that carried real content joined fine.
+        //
+        // The content now comes across. Sharing the SOURCE's object is still
+        // wrong, but that is prevented by copying it under the clone's own name
+        // rather than by having no blob at all — see
+        // RoomCloneShapeTests.Clone_does_not_reference_the_source_rooms_blob,
+        // which runs with a real object store. This suite has none, so the
+        // copy deliberately falls back to keeping the reference and only the
+        // "has content" half is checkable here.
+        await AssertBlobsAsync(firstCloneId, expectEmpty: false,
+            "a clone of a first-party template must carry its content");
 
         // Simulate the player saving MakerPen edits into their clone.
         var editedBlob = $"room_{firstCloneId}_edit_{Guid.NewGuid():N}.dat";