Session: blur, background contrast and animations off by default

The nested kwinrc had no [Plugins] group, so KWin ran its default blur and background
contrast effects, and kdeglobals had no AnimationDurationFactor, so animations ran at
full length. KWin renders through zink on Turnip, on the GPU vrcompositor needs, and
blur re-renders what's behind every translucent panel and menu; each animation frame is
another frame for KWin and ft-screens.

Before KWin starts, the session script now writes [Plugins] blurEnabled=false and
contrastEnabled=false to $XDG_CONFIG_HOME/kwinrc and [KDE] AnimationDurationFactor=0 to
its kdeglobals, each only if the desktop's own file has no value for it. It does this
once and records that in $XDG_CONFIG_HOME/frametoprc ([Defaults] effects=1), because
System Settings deletes a key put back to its default: without the marker, turning blur
back on wouldn't survive a restart. The ids blur and contrast are the built-in effects
of KWin 6.2.5 on SteamOS (both enabled by default in its plugin metadata). Tested
against a temporary XDG_CONFIG_HOME: fresh config, an existing blurEnabled=true kept,
and a deleted key not rewritten.

README and docs/reference.md say how to turn them back on.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

session/frametop-session.sh

@@ -234,6 +234,23 @@ elif [ "$(kreadconfig6 --file "$kwinrc" --group org.kde.kdecoration2 --key theme
   kwriteconfig6 --file "$kwinrc" --group org.kde.kdecoration2 --key theme --delete
 fi
 
+# KWin draws through zink on the headset's GPU, which vrcompositor needs, so the blur and
+# background contrast behind panels and menus and the window animations cost frames for
+# little. They're off by default in this desktop. Each is written once, before KWin first
+# reads it, and only if this desktop's config doesn't have it yet; the marker keeps it
+# from coming back, since System Settings deletes a setting put back to KDE's default.
+# docs/reference.md says how to turn them on again.
+default() {  # file group key value
+  [ -n "$(kreadconfig6 --file "$1" --group "$2" --key "$3")" ] || kwriteconfig6 --file "$1" --group "$2" --key "$3" "$4"
+}
+frametoprc=$XDG_CONFIG_HOME/frametoprc
+if [ "$(kreadconfig6 --file "$frametoprc" --group Defaults --key effects)" != 1 ]; then
+  default "$kwinrc" Plugins blurEnabled false
+  default "$kwinrc" Plugins contrastEnabled false
+  default "$XDG_CONFIG_HOME/kdeglobals" KDE AnimationDurationFactor 0
+  kwriteconfig6 --file "$frametoprc" --group Defaults --key effects 1
+fi
+
 # Profiles reopen apps (docs/profiles.md), so Plasma's own session restore stays off here;
 # with both, apps would open twice.
 kwriteconfig6 --file "$XDG_CONFIG_HOME/ksmserverrc" --group General --key loginMode emptySession