feat(D.2b): controls.ini stylesheet loader + apply title color

Adds ControlsIni — a minimal flat-INI reader for retail's controls.ini
(#AARRGGBB alpha-first color tokens; case-insensitive section/key lookup;
missing file returns an empty sheet with no throw). Wires the [title]
color token into the vitals panel's UiLabel in GameWindow.OnLoad, with
hardcoded white as the fallback. Visually a no-op (retail's [title] color
is white), but proves the stylesheet plumbing end-to-end (D.2b §7).
Three unit tests cover section parsing, #AARRGGBB decode, and graceful
missing-file handling.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -1748,12 +1748,20 @@ public sealed class GameWindow : IDisposable
                 return (t, w, h);
             }
 
+            // Phase D.2b — optional retail stylesheet. controls.ini lives under
+            // the AC install (ACDREAM_AC_DIR); absent → source-verified fallback.
+            var controls = _options.AcDir is { } acDir
+                ? AcDream.App.UI.ControlsIni.Load(System.IO.Path.Combine(acDir, "controls", "controls.ini"))
+                : AcDream.App.UI.ControlsIni.Parse(string.Empty);
+            var titleColor = controls.TryColor("title", "color", out var tc)
+                ? tc : new System.Numerics.Vector4(1f, 1f, 1f, 1f);
+
             var panel = new AcDream.App.UI.UiNineSlicePanel(ResolveChrome)
             { Left = 10, Top = 30, Width = 220, Height = 96 };
             panel.AddChild(new AcDream.App.UI.UiLabel
             {
                 Text = "Vitals", Left = 8, Top = 4,
-                TextColor = new System.Numerics.Vector4(1f, 1f, 1f, 1f),
+                TextColor = titleColor,
             });
 
             var vm = _vitalsVm!;

src/AcDream.App/UI/ControlsIni.cs

@@ -0,0 +1,65 @@
+using System.Collections.Generic;
+using System.Globalization;
+using System.Numerics;
+
+namespace AcDream.App.UI;
+
+/// <summary>
+/// Minimal reader for retail's <c>controls.ini</c> — a flat INI with one
+/// <c>[section]</c> per element type. Colors are <c>#AARRGGBB</c> (alpha
+/// first). Optional: a missing file yields an empty sheet (callers fall back
+/// to hardcoded defaults). See the D.2b spec §7.
+/// </summary>
+public sealed class ControlsIni
+{
+    private readonly Dictionary<string, Dictionary<string, string>> _sections;
+
+    private ControlsIni(Dictionary<string, Dictionary<string, string>> s) => _sections = s;
+
+    /// <summary>Load from disk; returns an empty sheet if the file is absent.</summary>
+    public static ControlsIni Load(string path)
+        => System.IO.File.Exists(path)
+            ? Parse(System.IO.File.ReadAllText(path))
+            : new ControlsIni(new());
+
+    public static ControlsIni Parse(string text)
+    {
+        var sections = new Dictionary<string, Dictionary<string, string>>(System.StringComparer.OrdinalIgnoreCase);
+        Dictionary<string, string>? cur = null;
+        foreach (var raw in text.Split('\n'))
+        {
+            var line = raw.Trim();
+            if (line.Length == 0 || line[0] == ';' || line[0] == '#') continue;
+            if (line[0] == '[' && line[^1] == ']')
+            {
+                var name = line[1..^1].Trim();
+                cur = new Dictionary<string, string>(System.StringComparer.OrdinalIgnoreCase);
+                sections[name] = cur;
+                continue;
+            }
+            int eq = line.IndexOf('=');
+            if (eq <= 0 || cur is null) continue;
+            cur[line[..eq].Trim()] = line[(eq + 1)..].Trim();
+        }
+        return new ControlsIni(sections);
+    }
+
+    public string? Get(string section, string key)
+        => _sections.TryGetValue(section, out var s) && s.TryGetValue(key, out var v) ? v : null;
+
+    /// <summary>Parse a <c>#AARRGGBB</c> token into an RGBA <see cref="Vector4"/>.</summary>
+    public bool TryColor(string section, string key, out Vector4 color)
+    {
+        color = default;
+        var v = Get(section, key);
+        if (v is null || v.Length != 9 || v[0] != '#') return false;
+        if (!uint.TryParse(v.AsSpan(1), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out uint argb))
+            return false;
+        float a = ((argb >> 24) & 0xFF) / 255f;
+        float r = ((argb >> 16) & 0xFF) / 255f;
+        float g = ((argb >> 8) & 0xFF) / 255f;
+        float b = (argb & 0xFF) / 255f;
+        color = new Vector4(r, g, b, a);
+        return true;
+    }
+}