fix Adwaita color-scheme enum: force-dark -> prefer-dark; drop unsupported GTK setting

Operator-flagged 2026-05-10:
  "Invalid color scheme force-dark (Expected one of: default,
   prefer-dark, prefer-light)"
  "Using GtkSettings:gtk-application-prefer-dark-theme with
   libadwaita is unsupported. Please use AdwStyleManager:color-scheme
   instead."

Two coupled corrections:

1. ADW_DEBUG_COLOR_SCHEME=force-dark -> prefer-dark across every
   flatpak override at /var/lib/flatpak/overrides/. The
   libadwaita-spec ADW_DEBUG_COLOR_SCHEME enum is
   {default, prefer-dark, prefer-light} -- "force-dark" was invented
   and rejected by libadwaita with the warning above. prefer-dark
   reaches the same intent (apps render dark theme on launch) via
   the supported API.

2. /etc/skel/.config/gtk-{3,4}.0/settings.ini: removed
   gtk-application-prefer-dark-theme=true. libadwaita explicitly
   ignores GtkSettings:gtk-application-prefer-dark-theme and warns
   on its use; theming flows through AdwStyleManager:color-scheme
   (which IS controlled by gsettings org.gnome.desktop.interface
    color-scheme=prefer-dark in /etc/dconf/db/local.d/00-mios-theme).
   gtk-theme-name=adw-gtk3-dark is retained -- it's the right knob
   for the GTK-only widget chrome that libadwaita doesn't override.

Author: Kabuki94

etc/skel/.config/gtk-3.0/settings.ini

@@ -3,7 +3,6 @@
 # new MiOS account. Operator-overridable per-user via GNOME Tweaks
 # or by editing ~/.config/gtk-3.0/settings.ini directly.
 [Settings]
-gtk-application-prefer-dark-theme=true
 gtk-theme-name=adw-gtk3-dark
 gtk-icon-theme-name=Adwaita
 gtk-cursor-theme-name=Adwaita

etc/skel/.config/gtk-4.0/settings.ini

@@ -3,7 +3,6 @@
 # new MiOS account. Operator-overridable per-user via GNOME Tweaks
 # or by editing ~/.config/gtk-3.0/settings.ini directly.
 [Settings]
-gtk-application-prefer-dark-theme=true
 gtk-theme-name=adw-gtk3-dark
 gtk-icon-theme-name=Adwaita
 gtk-cursor-theme-name=Adwaita

var/lib/flatpak/overrides/app.devsuite.Ptyxis

@@ -7,6 +7,6 @@ LIBGL_ALWAYS_SOFTWARE=1
 GALLIUM_DRIVER=llvmpipe
 LIBGL_KOPPER_DISABLE=1
 WEBKIT_DISABLE_COMPOSITING_MODE=1
-ADW_DEBUG_COLOR_SCHEME=force-dark
+ADW_DEBUG_COLOR_SCHEME=prefer-dark
 GDK_DPI_SCALE=0.75
 QT_FONT_DPI=72

var/lib/flatpak/overrides/com.mattjakeman.ExtensionManager

@@ -7,6 +7,6 @@ LIBGL_ALWAYS_SOFTWARE=1
 GALLIUM_DRIVER=llvmpipe
 LIBGL_KOPPER_DISABLE=1
 WEBKIT_DISABLE_COMPOSITING_MODE=1
-ADW_DEBUG_COLOR_SCHEME=force-dark
+ADW_DEBUG_COLOR_SCHEME=prefer-dark
 GDK_DPI_SCALE=0.75
 QT_FONT_DPI=72

var/lib/flatpak/overrides/org.gnome.Epiphany

@@ -7,6 +7,6 @@ LIBGL_ALWAYS_SOFTWARE=1
 GALLIUM_DRIVER=llvmpipe
 LIBGL_KOPPER_DISABLE=1
 WEBKIT_DISABLE_COMPOSITING_MODE=1
-ADW_DEBUG_COLOR_SCHEME=force-dark
+ADW_DEBUG_COLOR_SCHEME=prefer-dark
 GDK_DPI_SCALE=0.75
 QT_FONT_DPI=72

var/lib/flatpak/overrides/org.gnome.Nautilus

@@ -7,6 +7,6 @@ LIBGL_ALWAYS_SOFTWARE=1
 GALLIUM_DRIVER=llvmpipe
 LIBGL_KOPPER_DISABLE=1
 WEBKIT_DISABLE_COMPOSITING_MODE=1
-ADW_DEBUG_COLOR_SCHEME=force-dark
+ADW_DEBUG_COLOR_SCHEME=prefer-dark
 GDK_DPI_SCALE=0.75
 QT_FONT_DPI=72

var/lib/flatpak/overrides/org.gnome.Nautilus.Devel

@@ -7,6 +7,6 @@ LIBGL_ALWAYS_SOFTWARE=1
 GALLIUM_DRIVER=llvmpipe
 LIBGL_KOPPER_DISABLE=1
 WEBKIT_DISABLE_COMPOSITING_MODE=1
-ADW_DEBUG_COLOR_SCHEME=force-dark
+ADW_DEBUG_COLOR_SCHEME=prefer-dark
 GDK_DPI_SCALE=0.75
 QT_FONT_DPI=72

var/lib/flatpak/overrides/org.gnome.Software

@@ -7,6 +7,6 @@ LIBGL_ALWAYS_SOFTWARE=1
 GALLIUM_DRIVER=llvmpipe
 LIBGL_KOPPER_DISABLE=1
 WEBKIT_DISABLE_COMPOSITING_MODE=1
-ADW_DEBUG_COLOR_SCHEME=force-dark
+ADW_DEBUG_COLOR_SCHEME=prefer-dark
 GDK_DPI_SCALE=0.75
 QT_FONT_DPI=72