feat(D.2b): MarkupDocument (XML -> UiElement tree); vitals panel from vitals.xml

Implements Task 8 of the D.2b retail-UI plan. MarkupDocument.Build() parses
KSML-style panel markup into a live UiNineSlicePanel subtree, resolving
{Binding} attribute expressions against a supplied object via reflection.
Color format is #AARRGGBB (alpha-first, matching controls.ini). Handles
<panel> root (geometry + optional title label) and <meter> children (fill,
label, bar color). Future element kinds (label, button, image) extend the
switch without touching existing code.

vitals.xml encodes the just-approved vitals panel layout (health red #FFC70D0D,
stamina gold #FFD49E1F, mana blue #FF1F33D9); ships next to the binary via
PreserveNewest csproj rule. GameWindow.cs drops the 35-line hand-built panel
block in favour of a 4-line File.ReadAllText + MarkupDocument.Build call —
identical tree, identical render, now data-driven.

2 new tests (Build_CreatesPanelWithMeterFillLabelAndGeometry,
Build_NullBindingValuesYieldNullFillAndLabel) + 11 total targeted green.

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

src/AcDream.App/AcDream.App.csproj

@@ -50,6 +50,11 @@
     <None Include="..\..\docs\research\data\spells.csv" Link="data\spells.csv">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <!-- Phase D.2b: KSML-style panel markup assets (vitals.xml etc.) ship
+         next to the binary so MarkupDocument.Build can load them at runtime. -->
+    <None Include="UI\assets\**\*.xml">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
   <ItemGroup>
     <!-- Build the smoke plugin first and copy it into plugins/AcDream.Plugins.Smoke/ -->

src/AcDream.App/Rendering/GameWindow.cs

@@ -1753,42 +1753,11 @@ public sealed class GameWindow : IDisposable
             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)
+            string vitalsXml = System.IO.File.ReadAllText(
-                ? tc : new System.Numerics.Vector4(1f, 1f, 1f, 1f);
+                System.IO.Path.Combine(AppContext.BaseDirectory, "UI", "assets", "vitals.xml"));
-
+            var panel = AcDream.App.UI.MarkupDocument.Build(vitalsXml, _vitalsVm!, ResolveChrome, controls);
-            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 = titleColor,
-            });
-
-            var vm = _vitalsVm!;
-            panel.AddChild(new AcDream.App.UI.UiMeter
-            {
-                Left = 8, Top = 24, Width = 200, Height = 14,
-                BarColor = new System.Numerics.Vector4(0.78f, 0.05f, 0.05f, 1f),   // health red
-                Fill  = () => vm.HealthPercent,
-                Label = () => (vm.HealthCurrent, vm.HealthMax) is (uint c, uint m) ? $"{c}/{m}" : null,
-            });
-            panel.AddChild(new AcDream.App.UI.UiMeter
-            {
-                Left = 8, Top = 44, Width = 200, Height = 14,
-                BarColor = new System.Numerics.Vector4(0.83f, 0.62f, 0.12f, 1f),   // stamina gold (retail; not cyan)
-                Fill  = () => vm.StaminaPercent,
-                Label = () => (vm.StaminaCurrent, vm.StaminaMax) is (uint c, uint m) ? $"{c}/{m}" : null,
-            });
-            panel.AddChild(new AcDream.App.UI.UiMeter
-            {
-                Left = 8, Top = 64, Width = 200, Height = 14,
-                BarColor = new System.Numerics.Vector4(0.12f, 0.20f, 0.85f, 1f),   // mana blue
-                Fill  = () => vm.ManaPercent,
-                Label = () => (vm.ManaCurrent, vm.ManaMax) is (uint c, uint m) ? $"{c}/{m}" : null,
-            });
-
             _uiHost.Root.AddChild(panel);
-            Console.WriteLine("[D.2b] retail UI active — vitals panel wired (render-only).");
+            Console.WriteLine("[D.2b] retail UI active — vitals panel from vitals.xml markup.");
         }
 
         // Phase N.4+N.5 — WB rendering pipeline foundation. The modern path is

src/AcDream.App/UI/MarkupDocument.cs

@@ -0,0 +1,118 @@
+using System;
+using System.Globalization;
+using System.Numerics;
+using System.Reflection;
+using System.Xml.Linq;
+
+namespace AcDream.App.UI;
+
+/// <summary>
+/// Parses our KSML-style panel markup (mirrors retail's ElementDesc fields)
+/// into a live <see cref="UiElement"/> subtree. <c>{Binding}</c> attribute
+/// values resolve against a supplied object by property name (reflection).
+/// This is the format the future LayoutDesc importer will emit. See D.2b spec §7.
+/// </summary>
+public static class MarkupDocument
+{
+    /// <param name="xml">Raw XML markup for a single panel.</param>
+    /// <param name="binding">Object whose public properties are bound to <c>{PropName}</c> attributes.</param>
+    /// <param name="resolve">Surface id → (GL handle, width, height) for chrome sprites.</param>
+    /// <param name="style">Optional controls.ini stylesheet for the title color.</param>
+    public static UiNineSlicePanel Build(
+        string xml, object binding, Func<uint, (uint, int, int)> resolve,
+        ControlsIni? style = null)
+    {
+        var root = XDocument.Parse(xml).Root ?? throw new FormatException("empty markup");
+        if (root.Name.LocalName != "panel")
+            throw new FormatException($"root must be <panel>, got <{root.Name.LocalName}>");
+
+        var panel = new UiNineSlicePanel(resolve)
+        {
+            Left   = F(root, "x"),
+            Top    = F(root, "y"),
+            Width  = F(root, "w"),
+            Height = F(root, "h"),
+        };
+
+        string? title = (string?)root.Attribute("title");
+        if (!string.IsNullOrEmpty(title))
+        {
+            Vector4 tc = style is not null && style.TryColor("title", "color", out var c) ? c : Vector4.One;
+            panel.AddChild(new UiLabel { Text = title, Left = 8, Top = 4, TextColor = tc });
+        }
+
+        foreach (var el in root.Elements())
+        {
+            switch (el.Name.LocalName)
+            {
+                case "meter":
+                    var cur = BindUint((string?)el.Attribute("cur"), binding);
+                    var max = BindUint((string?)el.Attribute("max"), binding);
+                    panel.AddChild(new UiMeter
+                    {
+                        Left     = F(el, "x"),
+                        Top      = F(el, "y"),
+                        Width    = F(el, "w"),
+                        Height   = F(el, "h"),
+                        BarColor = Color((string?)el.Attribute("color")),
+                        Fill     = BindFloat((string?)el.Attribute("fill"), binding),
+                        Label    = () => (cur(), max()) is (uint c, uint m) ? $"{c}/{m}" : null,
+                    });
+                    break;
+                // future element kinds (label, button, image) added here
+            }
+        }
+        return panel;
+    }
+
+    private static float F(XElement e, string attr)
+        => float.TryParse((string?)e.Attribute(attr), NumberStyles.Float,
+            CultureInfo.InvariantCulture, out var v) ? v : 0f;
+
+    /// <summary>
+    /// Parses <c>#AARRGGBB</c> → RGBA <see cref="Vector4"/> (alpha first, matching
+    /// controls.ini convention). Falls back to opaque white on bad input.
+    /// </summary>
+    private static Vector4 Color(string? hex)
+    {
+        if (hex is { Length: 9 } && hex[0] == '#'
+            && uint.TryParse(hex.AsSpan(1), NumberStyles.HexNumber,
+                             CultureInfo.InvariantCulture, out uint argb))
+            return new Vector4(
+                ((argb >> 16) & 0xFF) / 255f,
+                ((argb >> 8)  & 0xFF) / 255f,
+                (argb         & 0xFF) / 255f,
+                ((argb >> 24) & 0xFF) / 255f);
+        return Vector4.One;
+    }
+
+    private static Func<float?> BindFloat(string? expr, object binding)
+    {
+        var pi = Prop(expr, binding);
+        if (pi is null) return () => 0f;
+        return () => pi.GetValue(binding) switch
+        {
+            float f  => f,
+            null     => (float?)null,
+            var v    => Convert.ToSingle(v, CultureInfo.InvariantCulture),
+        };
+    }
+
+    private static Func<uint?> BindUint(string? expr, object binding)
+    {
+        var pi = Prop(expr, binding);
+        if (pi is null) return () => null;
+        return () => pi.GetValue(binding) switch
+        {
+            uint u => u,
+            null   => (uint?)null,
+            var v  => Convert.ToUInt32(v, CultureInfo.InvariantCulture),
+        };
+    }
+
+    private static PropertyInfo? Prop(string? expr, object binding)
+    {
+        if (expr is null || expr.Length < 3 || expr[0] != '{' || expr[^1] != '}') return null;
+        return binding.GetType().GetProperty(expr[1..^1]);
+    }
+}

src/AcDream.App/UI/assets/vitals.xml

@@ -0,0 +1,5 @@
+<panel id="acdream.vitals" x="10" y="30" w="220" h="96" title="Vitals">
+  <meter id="health"  x="8" y="24" w="200" h="14" fill="{HealthPercent}"  cur="{HealthCurrent}"  max="{HealthMax}"  color="#FFC70D0D"/>
+  <meter id="stamina" x="8" y="44" w="200" h="14" fill="{StaminaPercent}" cur="{StaminaCurrent}" max="{StaminaMax}" color="#FFD49E1F"/>
+  <meter id="mana"    x="8" y="64" w="200" h="14" fill="{ManaPercent}"    cur="{ManaCurrent}"    max="{ManaMax}"    color="#FF1F33D9"/>
+</panel>

tests/AcDream.App.Tests/UI/MarkupDocumentTests.cs

@@ -0,0 +1,50 @@
+using AcDream.App.UI;
+
+namespace AcDream.App.Tests.UI;
+
+public class MarkupDocumentTests
+{
+    private sealed class FakeBinding
+    {
+        public float HealthPercent => 0.5f;
+        public uint? HealthCurrent => 109;
+        public uint? HealthMax => 218;
+        public float? ManaPercent => null;
+        public uint? ManaCurrent => null;
+        public uint? ManaMax => null;
+    }
+
+    [Fact]
+    public void Build_CreatesPanelWithMeterFillLabelAndGeometry()
+    {
+        const string xml =
+            "<panel id=\"acdream.vitals\" x=\"10\" y=\"30\" w=\"220\" h=\"96\" title=\"Vitals\">" +
+            "  <meter id=\"health\" x=\"8\" y=\"24\" w=\"200\" h=\"14\" fill=\"{HealthPercent}\" cur=\"{HealthCurrent}\" max=\"{HealthMax}\" color=\"#FFFF0000\"/>" +
+            "</panel>";
+
+        var panel = MarkupDocument.Build(xml, new FakeBinding(), _ => ((uint)1, 32, 32));
+
+        Assert.IsType<UiNineSlicePanel>(panel);
+        Assert.Equal(10f, panel.Left);
+        Assert.Equal(220f, panel.Width);
+        Assert.Equal(2, panel.Children.Count);            // title UiLabel + 1 meter
+        var meter = Assert.IsType<UiMeter>(panel.Children[1]);
+        Assert.Equal(8f, meter.Left);
+        Assert.Equal(200f, meter.Width);
+        Assert.Equal(0.5f, meter.Fill());
+        Assert.Equal("109/218", meter.Label());
+    }
+
+    [Fact]
+    public void Build_NullBindingValuesYieldNullFillAndLabel()
+    {
+        const string xml =
+            "<panel id=\"v\" x=\"0\" y=\"0\" w=\"10\" h=\"10\" title=\"V\">" +
+            "  <meter id=\"mana\" x=\"0\" y=\"0\" w=\"10\" h=\"2\" fill=\"{ManaPercent}\" cur=\"{ManaCurrent}\" max=\"{ManaMax}\" color=\"#FF0000FF\"/>" +
+            "</panel>";
+        var panel = MarkupDocument.Build(xml, new FakeBinding(), _ => ((uint)1, 32, 32));
+        var meter = Assert.IsType<UiMeter>(panel.Children[1]);
+        Assert.Null(meter.Fill());
+        Assert.Null(meter.Label());
+    }
+}