feat(ui): importer Fix 5 — build meter text children; drop character XP injection hacks

LayoutImporter.BuildWidget gains a UiMeter-specific branch after the
ConsumesDatChildren gate: Type-3 slice containers (already consumed by
DatWidgetFactory.BuildMeter to extract sprite ids) are skipped, but all
other children (Type-12 UIElement_Text overlays) are built normally,
registered in byId, and attached as UiElement children of the meter.

This fixes the XP meter (0x10000236): its two Type-12 children
  0x10000237 "XP for next level:" label
  0x10000238 XP-to-next-level value
are now real UiText widgets in the tree, findable via FindElement.

CharacterStatController.Bind now uses FindElement + LinesProvider binding
instead of injecting runtime AddChild nodes. The two previously-injected
UiText overlays are removed; the controller binds Padding=0, ClickThrough,
RightAligned on the dat-origin widgets instead.

New constants XpNextLabelId + XpNextValueId replace the old comment block.

TAB GROUPS (SKIPPED — documented): UiText.ConsumesDatChildren flipping is
NOT safe globally (risks chat/vitals) and the page-visibility pass in
CharacterStatController depends on tab group Children.Count==0. Tab sprite
injection onto layout.Root stays and is explicitly commented as deliberate.

VITALS SAFE: health/stamina/mana meters have only Type-3 children → new
loop finds nothing → zero UiElement children added → byte-identical render.
VitalsController.BindMeter AddChild(number) pattern unchanged.

Tests: 3 new LayoutImporterTests (slice-only, Fix-5 text children,
vitals regression guard) + 3 CharacterStatControllerTests (label bound,
value bound, missing children no-throw). 715 tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/AcDream.App.Tests/UI/Layout/CharacterStatControllerTests.cs

@@ -825,6 +825,78 @@ public class CharacterStatControllerTests
     public void Bind_MissingElements_DoesNotThrow()
         => CharacterStatController.Bind(Fake(), SampleData.SampleCharacter);
 
+    // ── Fix 5: XP meter text children bound via FindElement ──────────────────
+
+    /// <summary>
+    /// Fix 5: the XP label (0x10000237) is a dat-origin UiText child of the XP meter
+    /// (now built by the importer). After Bind(), FindElement must return a UiText with
+    /// a LinesProvider that emits "XP for next level:".
+    /// </summary>
+    [Fact]
+    public void Bind_XpMeter_XpNextLabel_IsBoundViaFindElement()
+    {
+        var meter    = new UiMeter();
+        var xpLabel  = new UiText();
+        // Attach the label as a child of the meter so it matches the real importer layout.
+        meter.AddChild(xpLabel);
+        var layout = Fake(
+            (CharacterStatController.XpMeterId,    meter),
+            (CharacterStatController.XpNextLabelId, xpLabel));
+
+        CharacterStatController.Bind(layout, SampleData.SampleCharacter);
+
+        Assert.NotNull(xpLabel.LinesProvider);
+        var lines = xpLabel.LinesProvider();
+        Assert.Single(lines);
+        Assert.Equal("XP for next level:", lines[0].Text);
+    }
+
+    /// <summary>
+    /// Fix 5: the XP value (0x10000238) is bound to the XpToNextLevel string.
+    /// ClickThrough=true and RightAligned=true must be set by the controller.
+    /// </summary>
+    [Fact]
+    public void Bind_XpMeter_XpNextValue_IsBoundViaFindElement()
+    {
+        var meter    = new UiMeter();
+        var xpValue  = new UiText();
+        meter.AddChild(xpValue);
+        var layout = Fake(
+            (CharacterStatController.XpMeterId,    meter),
+            (CharacterStatController.XpNextValueId, xpValue));
+
+        CharacterStatController.Bind(layout, SampleData.SampleCharacter);
+
+        Assert.NotNull(xpValue.LinesProvider);
+        Assert.True(xpValue.ClickThrough, "XP value overlay must be ClickThrough");
+        Assert.True(xpValue.RightAligned, "XP value overlay must be RightAligned");
+
+        var lines = xpValue.LinesProvider();
+        Assert.Single(lines);
+        // XpToNextLevel from SampleData = 42_000_000L formatted as "42,000,000"
+        Assert.Equal((42_000_000L).ToString("N0"), lines[0].Text);
+    }
+
+    /// <summary>
+    /// Fix 5: if XpNextLabelId / XpNextValueId are absent from the layout (the old
+    /// ConsumesDatChildren path, or a test layout that doesn't include them), Bind()
+    /// must not throw — the meter Fill is still bound.
+    /// </summary>
+    [Fact]
+    public void Bind_XpMeter_MissingTextChildren_DoesNotThrow()
+    {
+        var meter  = new UiMeter();
+        var layout = Fake((CharacterStatController.XpMeterId, meter));
+
+        // No XpNextLabelId or XpNextValueId in the layout.
+        var ex = Record.Exception(() =>
+            CharacterStatController.Bind(layout, SampleData.SampleCharacter));
+
+        Assert.Null(ex);
+        // Fill must still be bound.
+        Assert.NotNull(meter.Fill());
+    }
+
     // ── Helpers ──────────────────────────────────────────────────────────────
 
     /// <summary>Manufacture a minimal UiButton with a fake ElementInfo (no dat sprites).</summary>