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/DenAgent/res/DenAgent.rc2

@@ -0,0 +1,13 @@
+//
+// DENAGENT.RC2 - resources Microsoft Visual C++ does not edit directly
+//
+
+#ifdef APSTUDIO_INVOKED
+	#error this file is not editable by Microsoft Visual C++
+#endif //APSTUDIO_INVOKED
+
+
+/////////////////////////////////////////////////////////////////////////////
+// Add manually edited resources here...
+
+/////////////////////////////////////////////////////////////////////////////