feat(chat): retail text style — two-plane glyph outlines, authored SpewBox/chat styles

Campaign CH round 4, user-gate items 1+2. Root cause: retail ships a
second (background) glyph atlas per font, dilated 2px on every side,
plus two border-pixel scalars (Font.NumHorizontalBorderPixels/
NumVerticalBorderPixels) that acdream's font reader never read — so
even the pre-existing outline parameter drew almost nothing once
enabled. Landed together (either half alone is a no-op or a
regression):

- UiDatFont carries BorderX/BorderY from the DAT font resource.
- UiRenderContext.DrawStringDat inflates the background blit's source
  and destination rect by that margin and restructures into retail's
  exact two-pass whole-string outline-then-fill model
  (UIElement_Text::DrawSelf), plus the 8-neighbour +-1px fallback for
  fonts with no background atlas. Corrects the stale "property 0xd"
  comment to the real ids, 0x21 (Outline) / 0x22 (OutlineColor).
- LayoutDesc property 0x21/0x22 import (ElementInfo.Outline/
  OutlineColor, LayoutImporter.ReadState, ElementReader.Merge/
  ApplyCanonicalLegacyProjection, DatWidgetFactory.BuildText) so every
  authored-outline element across the DAT set is correct at once.
- SpewBox: RetailFontId corrected from a round-3 heuristic
  (0x40000025) to the actually-authored 0x40000001 (18px bold serif),
  Outline=true set on the controller's UiText. Fill colour stays the
  user-gate-round-1-pinned yellow — font atlases are alpha-only
  (PFID_A8), so there is no baked shading that could explain the
  screenshot's gold as anything other than the outline itself.
- Chat transcript: default fill now seeds from its authored
  ARGB(255,204,204,204) instead of an unrelated color-table slot
  (ChatTranscriptRenderer.BuildLines takes the transcript's own
  DefaultColor as a parameter); the 34-entry LogTextType table is
  untouched, and every existing CH1 conformance test stays green
  unmodified.

Regenerated the committed chat_2100006f.json fixture from the real
installed DAT, confirming end to end (not by missing-field default)
that the transcript carries no outline.

Tests: font-reader border fields + inflation math pinned against the
real DAT font, two-pass draw ordering/tint/inflation via a new
TextRenderer.DebugSpriteSegmentVerts test seam, property 0x21/0x22
import at both the ElementReader.Merge and StateDesc-property layers,
SpewBox font/outline, and the chat default-shade seed with the color
table proven untouched.

Full Release suite: 12,610 passed / 4 skipped / 0 failed
(AcDream.slnx, complete solution).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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

@@ -1,6 +1,9 @@
 using System.Collections.Generic;
 using System.Linq;
+using System.Numerics;
 using AcDream.App.UI.Layout;
+using AcDream.Core.Chat;
+using AcDream.UI.Abstractions.Panels.Chat;
 
 namespace AcDream.App.Tests.UI.Layout;
 
@@ -86,4 +89,78 @@ public class ChatTranscriptRendererTests
 
         Assert.Equal(new[] { "first", "", "third" }, lines);
     }
+
+    // ── BuildLines: default-color seed (Campaign CH round 4, Fix 5) ─────────
+    // docs/research/2026-08-10-retail-ui-text-style.md §5.2 Fix 5: the seed for
+    // a line whose LogTextType falls OUTSIDE RetailChatColorTable's 34 entries
+    // must be the ELEMENT's own authored default fill (the transcript's
+    // UiText.DefaultColor), not the color table's own index-0x00 slot. Every
+    // line with an IN-RANGE type must still resolve its OWN exact table color —
+    // this parameter must never perturb that half.
+
+    private static float MeasureByWidth(string s) => s.Length;
+
+    private static readonly Vector4 OffWhite = new(0.8f, 0.8f, 0.8f, 1f); // ARGB(255,204,204,204)
+
+    [Fact]
+    public void BuildLines_InRangeLogTextType_AlwaysUsesItsOwnTableColor_RegardlessOfDefaultColor()
+    {
+        // The 34-entry table remains the per-message color authority — this is
+        // the regression guard the task explicitly calls for: an in-range type
+        // (0x02 Speech -> pure white) must resolve to the SAME color whether the
+        // caller passes the new authored off-white default or an unrelated color.
+        var lines = new[] { new FormattedLine("hello", ChatKind.LocalSpeech, null, LogTextType: 0x02u) };
+
+        var withOffWhiteDefault = ChatTranscriptRenderer.BuildLines(lines, 1000f, MeasureByWidth, null, OffWhite);
+        var withUnrelatedDefault = ChatTranscriptRenderer.BuildLines(
+            lines, 1000f, MeasureByWidth, null, new Vector4(0f, 1f, 0f, 1f));
+
+        Assert.True(RetailChatColorTable.TryGetColor(0x02u, out Vector4 expected));
+        Assert.Equal(expected, Assert.Single(withOffWhiteDefault).Color);
+        Assert.Equal(expected, Assert.Single(withUnrelatedDefault).Color);
+    }
+
+    [Fact]
+    public void BuildLines_OutOfRangeLogTextType_AsFirstLine_UsesTheSuppliedDefaultColor()
+    {
+        // A LogTextType >= 34 (RetailChatColorTable.Colors.Count) is the
+        // out-of-range carry-forward case (see RetailChatColorTable's own doc):
+        // as the very FIRST line, there is no prior color to carry, so the
+        // element's own authored default fill applies — not colorGreen (the
+        // color table's unrelated 0x00 "Default" slot, the pre-fix seed).
+        var lines = new[] { new FormattedLine("mystery", ChatKind.System, null, LogTextType: 0xFFu) };
+
+        var result = ChatTranscriptRenderer.BuildLines(lines, 1000f, MeasureByWidth, null, OffWhite);
+
+        Assert.Equal(OffWhite, Assert.Single(result).Color);
+    }
+
+    [Fact]
+    public void BuildLines_OutOfRangeLogTextType_AfterAnInRangeLine_CarriesForwardThePriorTableColor()
+    {
+        // Retail's carry-forward rule (color-table doc §3.2): an out-of-range
+        // type leaves m_curFontColor UNCHANGED — it inherits whatever the
+        // PREVIOUS line resolved to, not the seed again. This must hold
+        // regardless of what defaultColor is passed.
+        var lines = new[]
+        {
+            new FormattedLine("says hi", ChatKind.LocalSpeech, null, LogTextType: 0x03u), // Tell -> yellow
+            new FormattedLine("mystery", ChatKind.System, null, LogTextType: 0xFFu),      // out of range
+        };
+
+        var result = ChatTranscriptRenderer.BuildLines(lines, 1000f, MeasureByWidth, null, OffWhite);
+
+        Assert.True(RetailChatColorTable.TryGetColor(0x03u, out Vector4 tellColor));
+        Assert.Equal(2, result.Count);
+        Assert.Equal(tellColor, result[0].Color);
+        Assert.Equal(tellColor, result[1].Color);   // carried forward, NOT OffWhite
+    }
+
+    [Fact]
+    public void BuildLines_EmptyDetailed_ReturnsEmpty_RegardlessOfDefaultColor()
+    {
+        var result = ChatTranscriptRenderer.BuildLines(
+            System.Array.Empty<FormattedLine>(), 1000f, MeasureByWidth, null, OffWhite);
+        Assert.Empty(result);
+    }
 }