fix(style): slower still -- the fade takes a third of a second now

The halved rates were still judged much too fast, so: 3/s in, 2/s out. Rise in
roughly 330ms, settle in 500ms. The textbook says hover fades live around 150ms;
the textbook does not play this game, and the person who does gets the vote.

Timing guard moved with it.

HellionChat/Util/HoverMath.cs

@@ -6,12 +6,14 @@ namespace HellionChat.Util;
 // Selune.cs:36-37).
 //
 // The rates started at 14/s in and 8/s out -- a full fade-in in seventy
-// milliseconds, which tester feedback called light speed. Half that now: rise in
-// about 150ms, settle in about 250ms, which is where UI fades usually live.
+// milliseconds, which tester feedback called light speed. The first correction
+// halved them and was still "much too fast", so: rise in about a third of a
+// second, settle in half of one. Textbook says 150ms; the textbook does not
+// play this game.
 internal static class HoverMath
 {
-    internal const float FadeInPerSecond = 6.5f;
-    internal const float FadeOutPerSecond = 4f;
+    internal const float FadeInPerSecond = 3f;
+    internal const float FadeOutPerSecond = 2f;
 
     // Below this an entry is indistinguishable from zero and can be dropped.
     internal const float EvictBelow = 0.001f;