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/DecalDat/DatFile.h

@@ -0,0 +1,76 @@
+// DatFile.h
+// Declaration of class cDatFile
+// Class for extracting data from portal.dat and cell.dat
+
+#ifndef __ACFILE_H
+#define __ACFILE_H
+
+#define FILE_COUNT   62
+
+class cDatFile
+{
+   // The AC File is created as a memory mapped file
+   // so we let the memory manager cache manage - it's also quite a bit nicer than
+   // code to seek/read everything
+   HANDLE m_hFile,
+      m_hMapping;
+   BYTE *m_pData;
+   DWORD m_dwSectorSize;
+
+public:
+   class cFile
+   {
+      BYTE *m_pFirstSector,
+         *m_pCurrentSector,
+         *m_pCurrentByte;
+      DWORD m_dwSize,
+         m_dwOffset;
+      cDatFile *m_pSource;
+
+   public:
+      // Locate the file in a directory
+
+      cFile( cDatFile *pSource, BYTE *pFirstSector, DWORD dwSize );
+
+      DWORD getSize() const
+      {
+         return m_dwSize;
+      }
+
+      DWORD tell() const
+      {
+         return m_dwOffset;
+      }
+
+      void reset();
+      DWORD read( BYTE *pbBuffer, DWORD dwSize );
+      DWORD skip( DWORD dwSize );
+   };
+
+   cDatFile( LPCTSTR szFilename, DWORD dwSectorSize = 256 );
+   ~cDatFile();
+
+   cFile getFile( DWORD dwFileNumber );
+
+   // Structures
+#pragma pack( push, 1 )
+   struct cFileEntry
+   {
+      DWORD m_dwID,
+         m_dwOffset,
+         m_dwSize;
+   };
+
+   struct cDirectory
+   {
+      DWORD m_subdirs[ FILE_COUNT ];
+      DWORD m_dwFiles;
+      cFileEntry m_files[ FILE_COUNT ];
+   };
+
+#pragma pack( pop )
+
+   friend cFile;
+};
+
+#endif