Rename to TNCat, add chip chase, G-codes and a Wayland layout

The project is now TNCat, after HEIDENHAIN's TNC controls. Binary, QML module
URI, settings path, bundle id and .desktop entry follow; the environment
switches are TNCAT_*.

Entertainment: a curled steel chip skitters in every minute or two, the cat
runs it down and bats it away a few times before sitting back looking pleased.
Mood changes flash the matching machine code above its head, G00 for a sprint,
G01 for a stroll, M08 while it washes, G28 for a stretch, M30 for a nap.

Window handling was split into two layouts. X11 and macOS keep one small window
per object, positioned by the app. Wayland gets a screen-filling overlay whose
input region is masked down to the cat, since a Wayland client cannot place its
own window. Overlay mode is automatic there and available elsewhere via
TNCAT_OVERLAY=1.

Also adds a ground-line setting so the cat can walk above a softkey row.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/platforminfo.h

@@ -2,9 +2,12 @@
 
 #include <QObject>
 #include <QQmlEngine>
+#include <QRectF>
 #include <QString>
+#include <QQuickWindow>
 
-// Small facts about the host that QML needs in order to pick window flags.
+// Small facts about the host that QML needs in order to pick window flags,
+// plus the input-region call that makes an overlay window click-through.
 class PlatformInfo : public QObject
 {
     Q_OBJECT
@@ -14,6 +17,7 @@ class PlatformInfo : public QObject
     Q_PROPERTY(QString name READ name CONSTANT)
     Q_PROPERTY(bool isX11 READ isX11 CONSTANT)
     Q_PROPERTY(bool isWayland READ isWayland CONSTANT)
+    Q_PROPERTY(bool overlayMode READ overlayMode CONSTANT)
     Q_PROPERTY(bool bypassWindowManager READ bypassWindowManager CONSTANT)
     Q_PROPERTY(bool opaqueBackground READ opaqueBackground CONSTANT)
 
@@ -24,16 +28,27 @@ public:
     bool isX11() const { return m_name == QLatin1String("xcb"); }
     bool isWayland() const { return m_name.startsWith(QLatin1String("wayland")); }
 
-    // WORKCAT_X11_BYPASS=1 turns the cat into an override-redirect window.
+    // Wayland forbids a client from placing its own window, so there the cat
+    // lives inside one screen-filling overlay and only moves within it.
+    // TNCAT_OVERLAY=1 forces the same mode elsewhere.
+    bool overlayMode() const { return m_overlay || isWayland(); }
+
+    // TNCAT_X11_BYPASS=1 turns the cat into an override-redirect window.
     // Useful on window managers that refuse to keep a Qt::Tool window on top.
     bool bypassWindowManager() const { return m_bypass; }
 
-    // WORKCAT_OPAQUE=1 paints a solid background instead of relying on a
+    // TNCAT_OPAQUE=1 paints a solid background instead of relying on a
     // compositor. Without compositing X11 renders transparency as black.
     bool opaqueBackground() const { return m_opaque; }
 
+    // Restricts the window's input region to one rectangle so clicks land on
+    // whatever is behind the rest of the overlay. Implemented by the X11 and
+    // Wayland plugins; a no-op on platforms that ignore the mask.
+    Q_INVOKABLE void setInputRegion(QQuickWindow *window, const QRectF &region);
+
 private:
     QString m_name;
+    bool m_overlay = false;
     bool m_bypass = false;
     bool m_opaque = false;
 };