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>

qml/ChipWindow.qml

@@ -0,0 +1,34 @@
+pragma ComponentBehavior: Bound
+import QtQuick
+import TNCat
+
+// The chip gets its own little click-through window so it can skitter away
+// from the cat across the whole screen.
+Window {
+    id: win
+
+    required property CatController cat
+    required property AppSettings settings
+
+    readonly property int chipSize: Math.round(settings.catSize * 0.45)
+
+    width: chipSize
+    height: Math.round(chipSize * 0.73)
+    x: cat.chipX - width / 2
+    y: Screen.desktopAvailableHeight - height - settings.bottomMargin
+    color: "transparent"
+    flags: Qt.FramelessWindowHint | Qt.WindowStaysOnTopHint | Qt.Tool
+           | Qt.NoDropShadowWindowHint | Qt.WindowDoesNotAcceptFocus
+           | Qt.WindowTransparentForInput
+           | (Platform.bypassWindowManager ? Qt.X11BypassWindowManagerHint : 0)
+    visible: cat.chipVisible && !Platform.opaqueBackground
+
+    Behavior on x {
+        NumberAnimation { duration: 320; easing.type: Easing.OutQuad }
+    }
+
+    Chip {
+        anchors.fill: parent
+        kick: win.cat.chipKick
+    }
+}