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/OverlayWindow.qml

@@ -0,0 +1,119 @@
+pragma ComponentBehavior: Bound
+import QtQuick
+import TNCat
+
+// One screen-filling, click-through window that holds the cat and the chip.
+// Wayland does not let a client place its own window, so there the cat moves
+// inside this overlay instead of the window moving across the desktop.
+Window {
+    id: win
+
+    required property CatController cat
+    required property AppSettings settings
+
+    signal settingsRequested()
+
+    // Fullscreen is a visibility, not a visible flag, so the mode switch has to
+    // go through visibility or the two fight each other.
+    property bool active: false
+
+    readonly property int catW: settings.catSize
+    readonly property int catH: Math.round(settings.catSize * 0.9)
+    readonly property real groundY: height - catH - settings.bottomMargin
+
+    // Only the cat itself should swallow clicks; everything else falls through.
+    function refreshInputRegion() {
+        Platform.setInputRegion(win, Qt.rect(Math.round(cat.x), Math.round(groundY), catW, catH))
+    }
+
+    visibility: active ? Window.FullScreen : Window.Hidden
+    color: "transparent"
+    flags: Qt.FramelessWindowHint | Qt.WindowStaysOnTopHint | Qt.Tool
+           | Qt.NoDropShadowWindowHint | Qt.WindowDoesNotAcceptFocus
+    title: qsTr("TNCat")
+
+    onActiveChanged: {
+        if (!active)
+            return
+        cat.stageWidth = width
+        cat.catWidth = catW
+        refreshInputRegion()
+    }
+    onWidthChanged: cat.stageWidth = width
+    onCatWChanged: cat.catWidth = catW
+
+    Binding {
+        target: win.cat
+        property: "catCenter"
+        value: Qt.point(win.x + win.cat.x + win.catW / 2, win.y + win.groundY + win.catH / 2)
+    }
+
+    // Coalesce mask updates: one X11 round trip per frame of walking is plenty.
+    Timer {
+        interval: 33
+        running: win.active
+        repeat: true
+        onTriggered: win.refreshInputRegion()
+    }
+
+    Chip {
+        x: win.cat.chipX - width / 2
+        y: win.height - height - win.settings.bottomMargin
+        width: Math.round(win.settings.catSize * 0.45)
+        height: Math.round(width * 0.73)
+        visible: win.cat.chipVisible
+        kick: win.cat.chipKick
+
+        Behavior on x {
+            NumberAnimation { duration: 320; easing.type: Easing.OutQuad }
+        }
+    }
+
+    Item {
+        id: catItem
+        x: win.cat.x
+        y: win.groundY
+        width: win.catW
+        height: win.catH
+
+        Cat {
+            anchors.fill: parent
+            coat: win.settings.coat
+            facingRight: win.cat.facingRight
+            mood: CatMoods.name(win.cat.mood)
+            lifted: win.cat.dragging
+            petted: win.cat.hovered && !win.cat.dragging
+            look: win.cat.look
+            showCodes: win.settings.showCodes
+
+            Accessible.role: Accessible.Button
+            Accessible.name: qsTr("TNCat")
+        }
+
+        HoverHandler {
+            onHoveredChanged: win.cat.hovered = hovered
+        }
+
+        DragHandler {
+            target: null
+            onActiveChanged: win.cat.dragging = active
+            onCentroidChanged: {
+                if (active)
+                    win.cat.x = Math.max(0, Math.min(win.cat.stageWidth - win.catW,
+                                                     catItem.x + centroid.position.x - centroid.pressPosition.x))
+            }
+        }
+
+        TapHandler {
+            acceptedButtons: Qt.LeftButton
+            onTapped: win.cat.pet()
+            onDoubleTapped: win.settingsRequested()
+            onLongPressed: win.settingsRequested()
+        }
+
+        TapHandler {
+            acceptedButtons: Qt.RightButton
+            onTapped: win.settingsRequested()
+        }
+    }
+}