test(style): pin the type scale table, and mark three mirrors

The arithmetic had tests from the first commit; the table in front of it did not.
Factors is indexed by the enum, so a role inserted in the middle shifts every
factor below it -- and each one still resolves to a plausible size, which is
exactly why nothing would have failed.

Three files were missing their TEST-MIRROR marker despite having mirrors. The
marker is how the drift check finds them.

HellionChat/Ui/StyleEngine/TypeScale.cs

@@ -7,6 +7,8 @@ internal enum TypeRole
     Meta,
 }
 
+// TEST-MIRROR: Ui/TypeScaleTests.cs
+//
 // Named sizes derived from one base, so a role means the same thing wherever it
 // is drawn.
 //

HellionChat/Ui/StyleEngine/Widgets/ChannelHeaderDetail.cs

@@ -2,6 +2,8 @@ using System.Globalization;
 
 namespace HellionChat.Ui.StyleEngine.Widgets;
 
+// TEST-MIRROR: Ui/ChannelHeaderDetailTests.cs
+//
 // Where you are and what time it is, as two parts rather than one string.
 //
 // They are split because they cannot share a face. The clock and a world name are

HellionChat/Util/LayoutFingerprint.cs

@@ -1,5 +1,7 @@
 namespace HellionChat.Util;
 
+// TEST-MIRROR: Util/LayoutFingerprintGateTests.cs
+//
 // Layout inputs that make a tab's cached row heights stale. Kept as a plain
 // value type so the build suite can pin the gate without an ImGui frame.
 internal readonly record struct LayoutFingerprint(