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/HotkeyImpl.cs

@@ -0,0 +1,120 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using Decal.Interop.Input;
+
+namespace Decal.DecalInput
+{
+    [ComVisible(true)]
+    [Guid("F183506A-3664-49D6-8CA4-CFD295F2811D")]
+    [ClassInterface(ClassInterfaceType.None)]
+    [ComSourceInterfaces(typeof(IHotkeyEvents))]
+    [ProgId("DecalInput.Hotkey")]
+    public class HotkeyImpl : IHotkey
+    {
+        private object _tag;
+        private int _vk = -1;
+        private bool _enabled;
+
+        public event IHotkeyEvents_HotkeyEventHandler Hotkey;
+
+        public object Tag
+        {
+            get => _tag;
+            set => _tag = value;
+        }
+
+        public string Key
+        {
+            get
+            {
+                if (_vk == -1) return string.Empty;
+                string name = KeyNames.NameFromVK(_vk);
+                return name != null ? "{" + name + "}" : ((char)_vk).ToString();
+            }
+            set
+            {
+                string s = value?.ToUpperInvariant();
+                if (string.IsNullOrEmpty(s)) return;
+
+                if (s[0] == '{')
+                {
+                    int end = s.IndexOf('}');
+                    if (end > 1)
+                    {
+                        string keyName = s.Substring(1, end - 1);
+                        int vk = KeyNames.VKFromName(keyName);
+                        if (vk >= 0) _vk = vk;
+                    }
+                }
+                else if (s.Length == 1)
+                {
+                    _vk = s[0];
+                }
+            }
+        }
+
+        public bool Enabled
+        {
+            get => _enabled;
+            set
+            {
+                if (value == _enabled) return;
+                _enabled = value;
+
+                if (InputServiceImpl.Instance != null)
+                {
+                    if (_enabled)
+                        InputServiceImpl.Instance.RegisterHotkey(this);
+                    else
+                        InputServiceImpl.Instance.UnregisterHotkey(this);
+                }
+            }
+        }
+
+        internal void FireHotkey()
+        {
+            Hotkey?.Invoke((Hotkey)(object)this);
+        }
+    }
+
+    internal static class KeyNames
+    {
+        private static readonly Dictionary<string, int> _nameToVK = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase)
+        {
+            {"BACKSPACE", 0x08}, {"BS", 0x08}, {"BKSP", 0x08},
+            {"CAPSLOCK", 0x14}, {"DELETE", 0x2E}, {"DEL", 0x2E},
+            {"DOWN", 0x28}, {"END", 0x23}, {"ENTER", 0x0D},
+            {"ESC", 0x1B}, {"HELP", 0x2F}, {"HOME", 0x24},
+            {"INS", 0x2D}, {"INSERT", 0x2D}, {"LEFT", 0x25},
+            {"NUMLOCK", 0x90}, {"PGDN", 0x22}, {"PGUP", 0x21},
+            {"PRTSC", 0x2C}, {"RIGHT", 0x27}, {"SCROLLLOCK", 0x91},
+            {"TAB", 0x09}, {"UP", 0x26},
+            {"F1", 0x70}, {"F2", 0x71}, {"F3", 0x72}, {"F4", 0x73},
+            {"F5", 0x74}, {"F6", 0x75}, {"F7", 0x76}, {"F8", 0x77},
+            {"F9", 0x78}, {"F10", 0x79}, {"F11", 0x7A}, {"F12", 0x7B},
+            {"F13", 0x7C}, {"F14", 0x7D}, {"F15", 0x7E}, {"F16", 0x7F},
+            {"+", 0x6B}, {"SHIFT", 0x10}, {"CTRL", 0x11}, {"ALT", 0x12},
+            {"LBUTTON", 0x01}, {"RBUTTON", 0x02}
+        };
+
+        private static readonly Dictionary<int, string> _vkToName;
+
+        static KeyNames()
+        {
+            _vkToName = new Dictionary<int, string>();
+            // Build reverse mapping, preferring longer names
+            foreach (var kvp in _nameToVK)
+            {
+                if (!_vkToName.ContainsKey(kvp.Value) || kvp.Key.Length > _vkToName[kvp.Value].Length)
+                    _vkToName[kvp.Value] = kvp.Key;
+            }
+        }
+
+        public static int VKFromName(string name) =>
+            _nameToVK.TryGetValue(name, out int vk) ? vk : -1;
+
+        public static string NameFromVK(int vk) =>
+            _vkToName.TryGetValue(vk, out string name) ? name : null;
+    }
+}