feat: chuva mode — moon, rain, lightning; clean transitions with balada

Rain mode with canvas rain, stormy sky, sun-to-moon transition and
lightning strobe. Mode switching fixed so only one of moon/globe shows:
file pollers are edge-triggered (stale /tmp files no longer fight),
toggle scripts keep the files mutually exclusive, exits fade fast while
entrances stay slow, drawGlobe solely owns globe opacity, and leaving
chuva restores the album-color theme on fog/horizon.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015HtPHsTnDcLVSCiF5FGHZj

plugin/contents/ui/config.qml

@@ -7,6 +7,8 @@ ColumnLayout {
     id: root
 
     property alias cfg_ShowSkeleton: skeletonCheck.checked
+    property alias cfg_BaladaMode:   baladaCheck.checked
+    property alias cfg_ChuvaMode:    chuvaCheck.checked
 
     spacing: Kirigami.Units.largeSpacing
 
@@ -18,5 +20,19 @@ ColumnLayout {
             Kirigami.FormData.label: i18n("Esqueleto:")
             text: i18n("Mostrar o robô dançando")
         }
+
+        CheckBox {
+            id: baladaCheck
+            Kirigami.FormData.label: i18n("Modo balada:")
+            text: i18n("Mirror ball + disco floor + refletores")
+            onCheckedChanged: if (checked) chuvaCheck.checked = false
+        }
+
+        CheckBox {
+            id: chuvaCheck
+            Kirigami.FormData.label: i18n("Modo chuva:")
+            text: i18n("Lua + chuva + relâmpagos")
+            onCheckedChanged: if (checked) baladaCheck.checked = false
+        }
     }
 }