Follow Plasma's virtual keyboard setting

KWin activates the input method for every text field; its policy (the
tray toggle) only gates the input panel, which sloposk doesn't use. sloposk
now asks KWin over D-Bus whether a focused field should show the
keyboard: never when off, only after touch or a pen by default.
"Always Show" and D-Bus Show/Toggle still show it.

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

src/app/KWinVirtualKeyboard.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <QObject>
+
+#include <functional>
+
+// KWin's virtual keyboard policy (the tray toggle, System Settings →
+// Virtual Keyboard): KWin activates the input method for every text field
+// and the policy only gates its input panel, which sloposk doesn't use, so
+// sloposk asks it over org.kde.KWin /VirtualKeyboard instead.
+class KWinVirtualKeyboard : public QObject
+{
+    Q_OBJECT
+
+public:
+    explicit KWinVirtualKeyboard(QObject *parent = nullptr);
+
+    // Calls `answer` with whether a field focused now should show the
+    // keyboard: never when it's off, only after touch or a pen in the
+    // default mode. True if KWin can't be asked.
+    void askShowOnActive(QObject *context, std::function<void(bool)> answer);
+
+Q_SIGNALS:
+    void modeChanged();
+};