Initial commit: Complete open-source Decal rebuild

All 5 phases of the open-source Decal rebuild:

Phase 1: 14 decompiled .NET projects (Interop.*, Adapter, FileService, DecalUtil)
Phase 2: 10 native DLLs rewritten as C# COM servers with matching GUIDs
  - DecalDat, DHS, SpellFilter, DecalInput, DecalNet, DecalFilters
  - Decal.Core, DecalControls, DecalRender, D3DService
Phase 3: C++ shims for Inject.DLL (D3D9 hooking) and LauncherHook.DLL
Phase 4: DenAgent WinForms tray application
Phase 5: WiX installer and build script

25 C# projects building with 0 errors.
Native C++ projects require VS 2022 + Windows SDK (x86).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Native/DecalFilters/Prefilter.rgs

@@ -0,0 +1,45 @@
+HKCR
+{
+	DecalFilters.Prefilter.1 = s 'Prefilter Class'
+	{
+		CLSID = s '{443D4A68-5422-4E0C-9460-973F8FBDB190}'
+	}
+	DecalFilters.Prefilter = s 'Prefilter Class'
+	{
+		CLSID = s '{443D4A68-5422-4E0C-9460-973F8FBDB190}'
+		CurVer = s 'DecalFilters.Prefilter.1'
+	}
+	NoRemove CLSID
+	{
+		ForceRemove {443D4A68-5422-4E0C-9460-973F8FBDB190} = s 'Prefilter Class'
+		{
+			ProgID = s 'DecalFilters.Prefilter.1'
+			VersionIndependentProgID = s 'DecalFilters.Prefilter'
+			ForceRemove 'Programmable'
+			InprocServer32 = s '%MODULE%'
+			{
+				val ThreadingModel = s 'Apartment'
+			}
+			'TypeLib' = s '{DA16DAA9-7F16-45D9-A59F-8C45A7F2ACB1}'
+		}
+	}
+}
+
+HKLM
+{
+   NoRemove SOFTWARE
+   {
+      NoRemove Decal
+      {
+         NoRemove Surrogates
+         {
+            ForceRemove {443D4A68-5422-4E0C-9460-973F8FBDB190} = s 'Prefilter Network Filter Surrogate'
+            {
+               val Enabled = d '1'
+               val Extension = s 'apn'
+               val Description = s 'Network Prefilter'
+            }
+         }
+      }
+   }
+}