feat(D.2b): vitals numbers as UiText (widget-generalization Task 8)

The vitals cur/max numbers now render through the generic UiText widget — retail
gmVitalsUI uses UIElement_Text for them, not a meter-internal label. VitalsController
attaches a centered, non-interactive UiText child to each meter and stops the meter
drawing its own label (UiMeter.Label -> null). New UiText.Centered draws the first line
centered H+V with the SAME formula UiMeter's overlay used, so the numbers are
pixel-identical — user-confirmed in the live client.

This completes the D.2b widget-generalization pass: every chat + vitals widget is now
built generically and registered to its retail Type (Button/Field*/Menu/Meter/Scrollbar/
Text), with thin find-by-id controllers. (*Field is controller-placed; Type 3 stays
UiDatElement for chrome.)

Divergence register: AP-37 vitals-numbers-via-UiMeter.Label clause retired. Full suite:
404 passed, 2 skipped, 0 failed.

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

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

@@ -28,7 +28,9 @@ public class VitalsBindingTests
             manaText:     () => "");
 
         Assert.Equal(0.42f, health.Fill()!.Value);
-        Assert.Equal("42/100", health.Label());
+        // The meter no longer draws its own label; the cur/max is a centered UiText child.
+        Assert.Null(health.Label());
+        Assert.Equal("42/100", NumberText(health));
     }
 
     // ── Test 2: All three meters wired to distinct providers ──────────────────
@@ -54,13 +56,13 @@ public class VitalsBindingTests
 
         // Each meter should reflect its own provider, not another's.
         Assert.Equal(0.25f, health.Fill()!.Value);
-        Assert.Equal("25/100", health.Label());
+        Assert.Equal("25/100", NumberText(health));
 
         Assert.Equal(0.50f, stamina.Fill()!.Value);
-        Assert.Equal("50/100", stamina.Label());
+        Assert.Equal("50/100", NumberText(stamina));
 
         Assert.Equal(0.75f, mana.Fill()!.Value);
-        Assert.Equal("75/100", mana.Label());
+        Assert.Equal("75/100", NumberText(mana));
     }
 
     // ── Test 3: Missing meter ids are silently skipped (no throw) ─────────────
@@ -87,6 +89,16 @@ public class VitalsBindingTests
 
     // ── Helpers ───────────────────────────────────────────────────────────────
 
+    /// <summary>The cur/max text from the centered <see cref="UiText"/> number that
+    /// <see cref="VitalsController"/> attaches as the meter's child.</summary>
+    private static string NumberText(UiMeter m)
+    {
+        var num = Assert.IsType<UiText>(m.Children[0]);
+        Assert.True(num.Centered);
+        var lines = num.LinesProvider();
+        return lines.Count > 0 ? lines[0].Text : "";
+    }
+
     private static ImportedLayout FakeLayout(params (uint id, UiElement e)[] items)
     {
         var dict = new Dictionary<uint, UiElement>();