Add window opacity slider to the Hellion theme

True per-window focus-aware transparency would require touching
ChatLogWindow and SettingsWindow individually (both upstream code,
both prone to cherry-pick churn). Instead expose a single opacity
slider that mixes a configured alpha into the WindowBg color in
PushGlobal — applies to every Hellion-rendered pane uniformly,
the game shines through, and form fields / dialogs / popups stay
opaque on top so input remains readable.

Default 92%, range clamped to 0.5–1.0 in the UI and 0x55–0xFF in
the alpha conversion so users can't accidentally make the panes
disappear entirely. Slider sits inside the Appearance section
right under the master Hellion-theme checkbox and is greyed out
when the theme is disabled.

ChatTwo/Resources/HellionStrings.Designer.cs

@@ -134,4 +134,6 @@ internal class HellionStrings
     internal static string Theme_Heading => Get(nameof(Theme_Heading));
     internal static string Theme_Enabled_Name => Get(nameof(Theme_Enabled_Name));
     internal static string Theme_Enabled_Description => Get(nameof(Theme_Enabled_Description));
+    internal static string Theme_WindowOpacity_Label => Get(nameof(Theme_WindowOpacity_Label));
+    internal static string Theme_WindowOpacity_Help => Get(nameof(Theme_WindowOpacity_Help));
 }

ChatTwo/Resources/HellionStrings.de.resx

@@ -273,4 +273,10 @@
   <data name="Theme_Enabled_Description" xml:space="preserve">
     <value>Industrielle HUD-Palette mit cyan-blauen Aktionsfarben, schiefer-violetten Tabs und Bernstein-Akzenten für aktive Zustände, global angewendet auf Chat-Fenster, Einstellungen, Viewer und Wizard. Deaktivieren, um das Standard-Dalamud-Erscheinungsbild zu nutzen.</value>
   </data>
+  <data name="Theme_WindowOpacity_Label" xml:space="preserve">
+    <value>Fenster-Deckkraft</value>
+  </data>
+  <data name="Theme_WindowOpacity_Help" xml:space="preserve">
+    <value>Wie deckend die Plugin-Fenster sind. Niedrigere Werte lassen das Spiel durchscheinen, Form-Felder und Dialoge bleiben oben drauf deckend und gut lesbar.</value>
+  </data>
 </root>

ChatTwo/Resources/HellionStrings.resx

@@ -273,4 +273,10 @@
   <data name="Theme_Enabled_Description" xml:space="preserve">
     <value>Industrial HUD palette with cyan-teal action accents, slate-violet tabs and amber active highlights, applied globally to chat log, settings, viewers and the wizard. Disable to fall back to the default Dalamud look.</value>
   </data>
+  <data name="Theme_WindowOpacity_Label" xml:space="preserve">
+    <value>Window opacity</value>
+  </data>
+  <data name="Theme_WindowOpacity_Help" xml:space="preserve">
+    <value>How opaque the plugin panes are. Lower values let the game shine through; form fields and dialogs stay opaque on top so they remain readable.</value>
+  </data>
 </root>