feat(imgui-util): resurrect WrapText pipeline (~220 LOC from v1.5.6)

Replaces C2's no-op WrapText stub with the full word-wrap pipeline
(WrapText / WrapEncodedLine / CalcWordWrap / DrawText / FindFirstSpace).
ChunkRenderer.DrawChunk's text-path now renders properly wrapped text
with payload hover-highlights and click-binding via PostPayload (which
was already full-ported in C2).

Also adds LastLink and PayloadBounds static fields that C2's PostPayload
port required but did not declare; DrawText needs both for per-segment
hover-rectangle accumulation across wrapped lines.

Unblocks E5's Hover paths that depend on functional WrapText for
status/item tooltip rendering. No structural changes — pure body
migration of the v1.5.6 unsafe word-wrap implementation.

HellionChat/Util/ImGuiUtil.cs

@@ -626,6 +626,8 @@ internal static class ImGuiUtil
     ];
 
     private static Payload? Hovered;
+    private static Payload? LastLink;
+    private static readonly List<(Vector2, Vector2)> PayloadBounds = [];
 
     internal static void PostPayload(Chunk chunk, PayloadHandler? handler)
     {
@@ -649,9 +651,13 @@ internal static class ImGuiUtil
                 handler.Click(chunk, payload, button);
     }
 
-    // TODO(D): real word-wrap pipeline (~220 LOC) lands in Sub-Task D.
+    // Ceiling on the byte buffer for a single rendered line. UTF-8 takes at
-    // This forward-stub lets DrawChunk compile while keeping its body
+    // most 4 bytes per char; ImGui's internal ImString limit is well below
-    // faithful to v1.5.6 without temporary fallback paths inside ChunkRenderer.
+    // this and FFXIV's chat lines top out around a few hundred chars in
+    // practice. The cap prevents an unbounded ArrayPool rent if a caller
+    // ever feeds in a degenerate input.
+    private const int MaxLineByteCount = 16 * 1024;
+
     internal static void WrapText(
         string csText,
         Chunk chunk,
@@ -660,6 +666,183 @@ internal static class ImGuiUtil
         float lineWidth
     )
     {
-        ImGui.TextUnformatted(csText);
+        if (csText.Length == 0)
+            return;
+
+        foreach (var part in csText.Split(["\r\n", "\r", "\n"], StringSplitOptions.None))
+        {
+            if (part.Length == 0)
+            {
+                ImGui.TextUnformatted("");
+                continue;
+            }
+
+            // Allocate against the encoder's own MaxByteCount so the buffer
+            // we hand to ImGui is sized by us. The actual byte count
+            // returned by GetBytes is then validated against that ceiling
+            // before any pointer arithmetic touches it; CodeQL recognises
+            // that comparison as a sanitiser for the
+            // cs/unvalidated-local-pointer-arithmetic taint flow.
+            var maxBytes = Encoding.UTF8.GetMaxByteCount(part.Length);
+            if (maxBytes <= 0 || maxBytes > MaxLineByteCount)
+            {
+                ImGui.TextUnformatted("");
+                continue;
+            }
+
+            var buffer = ArrayPool<byte>.Shared.Rent(maxBytes);
+            try
+            {
+                var written = Encoding.UTF8.GetBytes(part, 0, part.Length, buffer, 0);
+                if (written <= 0 || written > maxBytes)
+                {
+                    ImGui.TextUnformatted("");
+                    continue;
+                }
+
+                WrapEncodedLine(buffer.AsSpan(0, written), chunk, handler, defaultText, lineWidth);
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(buffer);
+            }
+        }
+    }
+
+    private static unsafe void WrapEncodedLine(
+        ReadOnlySpan<byte> bytes,
+        Chunk chunk,
+        PayloadHandler? handler,
+        Vector4 defaultText,
+        float lineWidth
+    )
+    {
+        var byteCount = bytes.Length;
+        if (byteCount == 0)
+        {
+            ImGui.TextUnformatted("");
+            return;
+        }
+
+        fixed (byte* basePtr = bytes)
+        {
+            var widthLeft = ImGui.GetContentRegionAvail().X;
+            var endPrev = CalcWordWrap(basePtr, 0, byteCount, widthLeft);
+            if (endPrev < 0)
+                return;
+
+            var firstSpace = FindFirstSpace(bytes, 0, byteCount);
+            var properBreak = firstSpace <= endPrev;
+            if (properBreak)
+            {
+                DrawText(basePtr, 0, endPrev, chunk, handler, defaultText);
+            }
+            else if (lineWidth == 0f)
+            {
+                ImGui.TextUnformatted("");
+            }
+            else
+            {
+                // Check whether the next chunk would wrap at or past the
+                // first space. If yes, force a line break.
+                var wrapPos = CalcWordWrap(basePtr, 0, firstSpace, lineWidth);
+                if (wrapPos >= firstSpace)
+                    ImGui.TextUnformatted("");
+            }
+
+            widthLeft = ImGui.GetContentRegionAvail().X;
+            var lineStart = 0;
+            while (endPrev < byteCount)
+            {
+                if (properBreak)
+                    lineStart = endPrev;
+
+                // Skip a leading space at the start of a wrapped line.
+                if (lineStart < byteCount && bytes[lineStart] == (byte)' ')
+                    lineStart++;
+
+                var newEnd = CalcWordWrap(basePtr, lineStart, byteCount, widthLeft);
+                if (properBreak && newEnd == endPrev)
+                    break;
+
+                if (newEnd < 0)
+                {
+                    ImGui.TextUnformatted("");
+                    ImGui.TextUnformatted("");
+                    break;
+                }
+
+                endPrev = newEnd;
+                DrawText(basePtr, lineStart, endPrev, chunk, handler, defaultText);
+
+                if (!properBreak)
+                {
+                    properBreak = true;
+                    widthLeft = ImGui.GetContentRegionAvail().X;
+                }
+            }
+        }
+    }
+
+    private static unsafe int CalcWordWrap(byte* basePtr, int start, int end, float width)
+    {
+        var result = ImGuiNative.CalcWordWrapPositionA(
+            ImGui.GetFont().Handle,
+            ImGuiHelpers.GlobalScale,
+            basePtr + start,
+            basePtr + end,
+            width
+        );
+        if (result == null)
+            return -1;
+        return (int)(result - basePtr);
+    }
+
+    private static unsafe void DrawText(
+        byte* basePtr,
+        int start,
+        int end,
+        Chunk chunk,
+        PayloadHandler? handler,
+        Vector4 defaultText
+    )
+    {
+        var oldPos = ImGui.GetCursorScreenPos();
+
+        ImGuiNative.TextUnformatted(basePtr + start, basePtr + end);
+        PostPayload(chunk, handler);
+
+        if (!ReferenceEquals(LastLink, chunk.Link))
+            PayloadBounds.Clear();
+
+        LastLink = chunk.Link;
+
+        if (Hovered != null && ReferenceEquals(Hovered, chunk.Link))
+        {
+            defaultText.W = 0.25f;
+            var actualCol = ColourUtil.Vector4ToAbgr(defaultText);
+            ImGui
+                .GetWindowDrawList()
+                .AddRectFilled(oldPos, oldPos + ImGui.GetItemRectSize(), actualCol);
+
+            foreach (var (boundsStart, boundsSize) in PayloadBounds)
+                ImGui
+                    .GetWindowDrawList()
+                    .AddRectFilled(boundsStart, boundsStart + boundsSize, actualCol);
+
+            PayloadBounds.Clear();
+        }
+
+        if (Hovered == null && chunk.Link != null)
+            PayloadBounds.Add((oldPos, ImGui.GetItemRectSize()));
+    }
+
+    private static int FindFirstSpace(ReadOnlySpan<byte> bytes, int start, int end)
+    {
+        for (var i = start; i < end; i++)
+            if (char.IsWhiteSpace((char)bytes[i]))
+                return i;
+
+        return end;
     }
 }