fix(ui): pass measured width straight through IconButton, drop broken subtract

Inspired by ChatTwo upstream f35b7d3 (Infiziert90, 2026-05-12).

Upstream dropped the width parameter entirely because nothing called
it. We keep the parameter — two ChatLogWindow header buttons (Cog,
EyeSlash) size themselves to match the preceding ChannelIcon button.

The actual bug is local: the previous size = width - 2 * CellPadding.X
mixed a raw int (HUD-scale unaware) with CellPadding.X (HUD-scaled),
so the button shrank under elevated HUD scale. ImGui.Button handles
its own frame padding internally, so the measured width passes
through unchanged.

HellionChat/Util/ImGuiUtil.cs

@@ -254,6 +254,17 @@ internal static class ImGuiUtil
         return end;
     }
 
+    // ---------------------------------------------------------------
+    // Inspired by ChatTwo upstream f35b7d3 (Infiziert90, 2026-05-12).
+    // Upstream dropped the width parameter (no callers there); we keep
+    // it because two ChatLogWindow header buttons size themselves to
+    // match the ChannelIcon button's frame. The actual bug is the
+    // manual size = width - 2 * CellPadding.X subtraction: CellPadding
+    // scales with HUD scale, the raw int does not, so the button
+    // shrank under high HUD scales. ImGui.Button already handles its
+    // own frame padding internally — pass the measured width straight
+    // through.
+    // ---------------------------------------------------------------
     internal static bool IconButton(
         FontAwesomeIcon icon,
         string? id = null,
@@ -268,10 +279,7 @@ internal static class ImGuiUtil
         bool ret;
         using (Plugin.FontManager.FontAwesome.Push())
         {
-            var size = Vector2.Zero;
+            var size = width > 0 ? new Vector2(width, 0f) : Vector2.Zero;
-            if (width > 0)
-                size.X = width - 2 * ImGui.GetStyle().CellPadding.X;
-
             ret = ImGui.Button(label, size);
         }