Radar: nearby_objects every second and dungeon_map per dungeon landblock

start_radar/stop_radar from the backend drive it, as before. nearby_objects
keeps the original's shape: map coordinates on the surface, landblock-local
raw positions with zero map coordinates in a dungeon, ids as signed ints, the
same eight object classes, no wielded items or self. dungeon_map is built the
original's way from the landblock's cells (x a multiple of 10, whole metres,
6-metre floors, rotation = the orientation's stored W) and sent once per
landblock per session; the cells come through a small reader that the
plugin API's dungeon-cell data will fill (until then the map is not sent).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/OpenAC.MosswartMassacre.Tests/Fakes/FakeAutomation.cs

@@ -42,6 +42,8 @@ public sealed class FakeAutomation : IAutomationSurface
 
     public FakeNetwork Network { get; } = new();
 
+    public FakeDungeonMap DungeonMap { get; } = new();
+
     ICharacterInfo IAutomationSurface.Character => Character;
     ISpellCatalog IAutomationSurface.Spells => Spells;
     IMagicCommands IAutomationSurface.Magic => Magic;
@@ -58,6 +60,7 @@ public sealed class FakeAutomation : IAutomationSurface
     IVendorAutomation IAutomationSurface.Vendor => Vendor;
     ILoginAutomation IAutomationSurface.Login => Login;
     INetworkAutomation IAutomationSurface.Network => Network;
+    IDungeonMapAutomation IAutomationSurface.DungeonMap => DungeonMap;
 }
 
 /// <summary>A settable <see cref="ITradeAutomation"/>: a test drives <see cref="Raise*"/> and inspects <see cref="Calls"/>.</summary>