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>

Managed/Decal.DecalInput/InputBufferImpl.cs

@@ -0,0 +1,74 @@
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using Decal.Interop.Input;
+
+namespace Decal.DecalInput
+{
+    [ComVisible(true)]
+    [Guid("F0A17A04-7F8F-4A17-A41D-8C297A1E929B")]
+    [ClassInterface(ClassInterfaceType.None)]
+    [ComSourceInterfaces(typeof(IInputBufferEvents))]
+    [ProgId("DecalInput.InputBuffer")]
+    public class InputBufferImpl : IInputBuffer
+    {
+        private object _tag;
+        private readonly List<string> _commands = new List<string>();
+        private bool _running;
+
+        public event IInputBufferEvents_BeginEventHandler Begin;
+        public event IInputBufferEvents_EndEventHandler End;
+        public event IInputBufferEvents_EventEventHandler Event;
+
+        public object Tag
+        {
+            get => _tag;
+            set => _tag = value;
+        }
+
+        public void Add(string Command)
+        {
+            _commands.Add(Command);
+        }
+
+        public void Push(string Command)
+        {
+            _commands.Insert(0, Command);
+        }
+
+        public void Pop()
+        {
+            if (_commands.Count > 0)
+                _commands.RemoveAt(_commands.Count - 1);
+        }
+
+        public bool CanRun => !_running && InputServiceImpl.Instance?.ActiveBuffer == null;
+
+        public void Run()
+        {
+            if (!CanRun) return;
+            _running = true;
+
+            if (InputServiceImpl.Instance != null)
+                InputServiceImpl.Instance.ActiveBuffer = this;
+
+            Begin?.Invoke((InputBuffer)(object)this);
+            // Actions would be processed in Render2D tick
+        }
+
+        public void Stop()
+        {
+            _running = false;
+
+            if (InputServiceImpl.Instance?.ActiveBuffer == this)
+                InputServiceImpl.Instance.ActiveBuffer = null;
+
+            End?.Invoke((InputBuffer)(object)this);
+            _commands.Clear();
+        }
+
+        internal void FireEvent(int eventId, object param)
+        {
+            Event?.Invoke((InputBuffer)(object)this, eventId, param);
+        }
+    }
+}