Add a coffee break

Every so often a mug appears at the cat's nose, it sits down, dips its head in
and takes a few slow sips while steam rises. M01, optional stop.

The mug lives in its own click-through window like the chip, or inside the
overlay on Wayland. It goes away as soon as the cat is petted, dragged, sent to
sleep or moves on to something else, so no mug is ever left standing.

Also renames OverlayWindow's mode flag, which shadowed QWindow::active.

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

CMakeLists.txt

@@ -22,7 +22,7 @@ qt_add_executable(tncat
 target_include_directories(tncat PRIVATE src)
 
 # QML files live in qml/ but register at the module root (TNCat.Main etc.)
-set(TNCAT_QML Main Cat Chip CatWindow ChipWindow OverlayWindow SettingsWindow CatMoods)
+set(TNCAT_QML Main Cat Chip Cup CatWindow ChipWindow CupWindow OverlayWindow SettingsWindow CatMoods)
 foreach(qmlfile IN LISTS TNCAT_QML)
     set_source_files_properties(qml/${qmlfile}.qml PROPERTIES QT_RESOURCE_ALIAS ${qmlfile}.qml)
     list(APPEND TNCAT_QML_FILES qml/${qmlfile}.qml)