test(D.2b): conformance polish — table-driven slice asserts + BOM-safe loader

Fix 1: replace 3 copy-paste meter blocks in VitalsTree_MetersHaveExpectedSliceIds
with a single table-driven loop — a 4th meter is now a one-liner and failures
name the failing meter id directly.

Fix 2: FixtureLoader now reads the fixture as bytes and strips the UTF-8 BOM
(EF BB BF) before passing the span to JsonSerializer, so a BOM-bearing fixture
file never causes a spurious JsonReaderException.

Fix 3: add [Trait("Category", "Conformance")] at the class level so conformance
tests are selectable by category filter.

Fix 4: add missing <param name="layoutId"> doc tag to LayoutImporter.ImportInfos.

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

src/AcDream.App/UI/Layout/LayoutImporter.cs

@@ -129,6 +129,8 @@ public static class LayoutImporter
     /// ElementInfo tree (no widgets). Exposed for fixture generation + conformance tests.
     /// Returns null if the layout is missing.
     /// </summary>
+    /// <param name="dats">The dat collection to read the LayoutDesc from.</param>
+    /// <param name="layoutId">The LayoutDesc dat id to read.</param>
     public static ElementInfo? ImportInfos(DatCollection dats, uint layoutId)
     {
         var ld = dats.Get<LayoutDesc>(layoutId);

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

@@ -29,9 +29,14 @@ public static class FixtureLoader
         if (!File.Exists(fixturePath))
             throw new FileNotFoundException($"Vitals fixture not found at: {fixturePath}");
 
-        var json = File.ReadAllText(fixturePath, System.Text.Encoding.UTF8);
+        var bytes = File.ReadAllBytes(fixturePath);
-        var root = JsonSerializer.Deserialize<ElementInfo>(json, _opts)
+        // Strip UTF-8 BOM (EF BB BF) if present so JsonSerializer.Deserialize<T>(ReadOnlySpan<byte>)
-            ?? throw new InvalidOperationException("Failed to deserialize vitals fixture.");
+        // does not reject the first byte.
+        ReadOnlySpan<byte> span = bytes;
+        if (span.Length >= 3 && span[0] == 0xEF && span[1] == 0xBB && span[2] == 0xBF)
+            span = span[3..];
+        var root = JsonSerializer.Deserialize<AcDream.App.UI.Layout.ElementInfo>(span, _opts)
+            ?? throw new InvalidOperationException($"fixture deserialized to null: {fixturePath}");
 
         return LayoutImporter.Build(root, _ => (0u, 0, 0), null);
     }

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

@@ -14,6 +14,7 @@ namespace AcDream.App.Tests.UI.Layout;
 ///
 /// Sprite ids sourced from <c>docs/research/2026-06-15-layoutdesc-format.md §11</c>.
 /// </summary>
+[Trait("Category", "Conformance")]
 public class LayoutConformanceTests
 {
     // ── Test 1: Three meters at expected rects ────────────────────────────────
@@ -58,40 +59,20 @@ public class LayoutConformanceTests
     {
         var layout = FixtureLoader.LoadVitals();
 
-        // Health bar
+        // Columns: MeterId, then 6 slice ids in order:
-        {
+        //   BackLeft, BackTile, BackRight, FrontLeft, FrontTile, FrontRight
-            var elem = layout.FindElement(0x100000E6u);
+        (uint MeterId, uint[] Slices)[] cases =
-            var m = Assert.IsType<UiMeter>(elem);
+        [
-            Assert.Equal(0x0600747Eu, m.BackLeft);
+            (0x100000E6u, [0x0600747Eu, 0x0600747Fu, 0x06007480u, 0x06007481u, 0x06007482u, 0x06007483u]), // health
-            Assert.Equal(0x0600747Fu, m.BackTile);
+            (0x100000ECu, [0x06007484u, 0x06007485u, 0x06007486u, 0x06007487u, 0x06007488u, 0x06007489u]), // stamina
-            Assert.Equal(0x06007480u, m.BackRight);
+            (0x100000EEu, [0x0600748Au, 0x0600748Bu, 0x0600748Cu, 0x0600748Du, 0x0600748Eu, 0x0600748Fu]), // mana
-            Assert.Equal(0x06007481u, m.FrontLeft);
+        ];
-            Assert.Equal(0x06007482u, m.FrontTile);
-            Assert.Equal(0x06007483u, m.FrontRight);
-        }
 
-        // Stamina bar
+        foreach (var (meterId, s) in cases)
         {
-            var elem = layout.FindElement(0x100000ECu);
+            var m = Assert.IsType<UiMeter>(layout.FindElement(meterId));
-            var m = Assert.IsType<UiMeter>(elem);
+            Assert.Equal(s[0], m.BackLeft);   Assert.Equal(s[1], m.BackTile);   Assert.Equal(s[2], m.BackRight);
-            Assert.Equal(0x06007484u, m.BackLeft);
+            Assert.Equal(s[3], m.FrontLeft);  Assert.Equal(s[4], m.FrontTile);  Assert.Equal(s[5], m.FrontRight);
-            Assert.Equal(0x06007485u, m.BackTile);
-            Assert.Equal(0x06007486u, m.BackRight);
-            Assert.Equal(0x06007487u, m.FrontLeft);
-            Assert.Equal(0x06007488u, m.FrontTile);
-            Assert.Equal(0x06007489u, m.FrontRight);
-        }
-
-        // Mana bar
-        {
-            var elem = layout.FindElement(0x100000EEu);
-            var m = Assert.IsType<UiMeter>(elem);
-            Assert.Equal(0x0600748Au, m.BackLeft);
-            Assert.Equal(0x0600748Bu, m.BackTile);
-            Assert.Equal(0x0600748Cu, m.BackRight);
-            Assert.Equal(0x0600748Du, m.FrontLeft);
-            Assert.Equal(0x0600748Eu, m.FrontTile);
-            Assert.Equal(0x0600748Fu, m.FrontRight);
         }
     }