feat(command-help-window): full R2 migration (ctor-injected + DI-reg)

J resurrects CommandHelpWindow from the v1.7.0 stub state:

- Class header public → internal sealed
- Ctor takes 4 DI deps (ChunkRenderer, MainWindow, InputBar, ILogger)
  via Factory-Lambda DI-reg. NO Lender<PayloadHandler> — command-help
  chunks are read-only command-description text with no click-targets
  (per spec §5-J + F W8 consumer audit).
- Draw() calls _chunkRenderer.DrawChunks(desc chunks, wrap: true,
  handler: null, lineWidth: 0f) — null-handler is intentional.
- Plugin.cs property visibility flipped public → internal to satisfy
  CS0053 (analogous to I's InputPreview fix).

K (R3 DebuggerWindow counters) and A2 (Lender + handler.Draw fix) are
the remaining Phase-3 sub-tasks before Polish-Sweep + Smoke-Gate.

HellionChat/Ui/CommandHelpWindow.cs

@@ -1,20 +1,37 @@
+using System.Numerics;
 using Dalamud.Bindings.ImGui;
+using Dalamud.Interface.Utility;
 using Dalamud.Interface.Windowing;
+using Dalamud.Utility;
+using HellionChat.Ui.Components;
+using HellionChat.Util;
 using Lumina.Text.ReadOnly;
+using Microsoft.Extensions.Logging;
 
 namespace HellionChat.Ui;
 
-// Slash-command help popup is offline while the chat input pipeline is
-// rebuilt. UpdateContent stays callable so the input layer can keep its
-// integration shape, but it always leaves the window closed for now.
-public class CommandHelpWindow : Window
+internal sealed class CommandHelpWindow : Window
 {
-    private readonly Plugin _plugin;
+    private readonly ChunkRenderer _chunkRenderer;
+    private readonly Windows.MainWindow _mainWindow;
+    private readonly Components.InputBar _inputBar;
+    private readonly ILogger<CommandHelpWindow> _logger;
 
-    internal CommandHelpWindow(Plugin plugin)
+    private ReadOnlySeString? _commandDescription;
+
+    public CommandHelpWindow(
+        ChunkRenderer chunkRenderer,
+        Windows.MainWindow mainWindow,
+        Components.InputBar inputBar,
+        ILogger<CommandHelpWindow> logger
+    )
         : base("command help##chat2-commandhelp")
     {
-        _plugin = plugin;
+        _chunkRenderer = chunkRenderer;
+        _mainWindow = mainWindow;
+        _inputBar = inputBar;
+        _logger = logger;
+
         Flags =
             ImGuiWindowFlags.NoSavedSettings
             | ImGuiWindowFlags.NoTitleBar
@@ -22,14 +39,59 @@ public class CommandHelpWindow : Window
             | ImGuiWindowFlags.NoResize
             | ImGuiWindowFlags.NoFocusOnAppearing
             | ImGuiWindowFlags.AlwaysAutoResize;
+
         RespectCloseHotkey = false;
         DisableWindowSounds = true;
+
+        // Logger injected for future diagnostic hooks (no call-sites yet in R2).
+        _ = _logger;
+        // InputBar injected for future integration (no call-sites yet in R2).
+        _ = _inputBar;
     }
 
     public void UpdateContent(ReadOnlySeString commandDesc)
     {
-        IsOpen = false;
+        _commandDescription = commandDesc;
+
+        var width = 350;
+        var scaledWidth = width * ImGuiHelpers.GlobalScale;
+        var pos = _mainWindow.LastWindowPos;
+        switch (Plugin.Config.CommandHelpSide)
+        {
+            case CommandHelpSide.Right:
+                pos.X += _mainWindow.LastWindowSize.X;
+                break;
+            case CommandHelpSide.Left:
+                pos.X -= scaledWidth;
+                break;
+            case CommandHelpSide.None:
+            default:
+                IsOpen = false;
+                return;
+        }
+
+        Position = pos;
+        SizeConstraints = new WindowSizeConstraints
+        {
+            // scaledWidth keeps size constraints in the same coordinate space as
+            // Position so the help window stays correct width at non-100% DPI.
+            MinimumSize = new Vector2(scaledWidth, 0),
+            MaximumSize = _mainWindow.LastWindowSize with { X = scaledWidth },
+        };
+
+        IsOpen = true;
     }
 
-    public override void Draw() { }
+    public override void Draw()
+    {
+        if (_commandDescription == null)
+            return;
+
+        var chunks = ChunkUtil
+            .ToChunks(_commandDescription.Value.ToDalamudString(), ChunkSource.None, null)
+            .ToList();
+
+        // Command-help chunks are read-only description text — no click-targets.
+        _chunkRenderer.DrawChunks(chunks, wrap: true, handler: null, lineWidth: 0f);
+    }
 }