## Summary
- `AnchoredItemSerializationTests.LastMovedAndDecayReset_RoundTripExactly` never deleted its deserialized copy. `Item.Deserialize` enters the item into its map's sectors, so the copy stayed live on Felucca at (121,100). `ItemEnumerator_FiltersByBoundsAndOrder`, `ItemByDistanceEnumerator_Bounds_FindsItemsInBounds` and `ItemByDistanceEnumerator_Bounds_MakeBoundsInclusive` scan that area and found an extra item whenever the serialization test ran before them, so they failed depending on test order. The copy is now deleted in a `finally`.
- Bump MailKit 4.17.0 → 4.18.0 and Microsoft.NET.Test.Sdk 18.10.0 → 18.10.1.
## Test plan
- [x] Probe test: a deserialized copy shows up in `GetItemsInBounds` (reproduced), and after the fix the area is empty
- [x] Server.Tests: 907/907 pass
- [x] UOContent.Tests: 1126 pass, 2 skipped
- [x] Solution builds with 0 errors
28c38168bc