fix: card-overview subtext wrap + v16 default bumps + chat-colour preset

UI:
- SettingsOverview cards now wrap subtext to two lines (DrawList wrap-
  width) and the card height grew from 96 to 110 px. Single-line
  fitting clipped most of the bilingual subtitles.
- HellionStyle pushes ChildBg with alpha 0 when WindowOpacity < 1.0
  to keep stacked BeginChild layers from compounding the deckgrade
  past what the slider suggests.
- WindowOpacity slider helpmarker now points to Dalamud's per-window
  hamburger menu for opacity / blur / pin / click-through overrides.

UX defaults (v15 → v16 migration adopts new values only when the user
is still on the previous default — bool flips are heuristic, the prior
defaults are from the v1.2.0 cycle and rarely toggled):
- UseCompactDensity false → true (single-line message style is cleaner)
- HideInNewGamePlusMenu false → true (consistent with other hide-flags)
- HideSameTimestamps false → true (cleaner log)
- MaxLinesToRender 5000 → 2500 (mid-range hardware friendlier)
- ChatColours empty → Hellion brand preset (the first-run wizard does
  not offer a preset choice, so fresh installs get the brand colours
  out of the box)

HellionChat/Ui/HellionStyle.cs

@@ -52,7 +52,18 @@ internal static class HellionStyle
 
         var alphaByte = (uint)Math.Clamp((int)(windowOpacity * 255f), 0x55, 0xFF);
         var windowBgWithAlpha = (c.WindowBg & 0xFFFFFF00u) | alphaByte;
-        var childBgWithAlpha  = (c.ChildBg  & 0xFFFFFF00u) | alphaByte;
+
+        // ChildBg-Alpha: Sub-Bereiche (Tab-Sidebar, Message-Area, Input-Bar)
+        // werden im ChatLog-Window als BeginChild gezeichnet. Würde der ChildBg
+        // mit dem gleichen Alpha wie WindowBg gerendert, multiplizieren sich
+        // die Layer (1 - (1-α)² Deckung), und 50 % WindowOpacity kommt mit
+        // 75 % Deckung im Child-Bereich an — das Fenster wirkt solider als der
+        // Slider verspricht. Bei voller Opacity bleibt der Theme-Akzent
+        // erhalten (Theme-eigene Alpha-Komponente, i.d.R. FF); sobald der User
+        // Transparenz zieht, wird ChildBg vollständig durchsichtig damit nur
+        // der WindowBg-Layer die finale Deckung bestimmt.
+        var childBgAlpha = windowOpacity >= 0.999f ? (c.ChildBg & 0xFFu) : 0u;
+        var childBgWithAlpha = (c.ChildBg & 0xFFFFFF00u) | childBgAlpha;
 
         // Layout
         stack.PushStyleVar(ImGuiStyleVar.WindowRounding,    l.WindowRounding);