feat: support named switchable layouts

fancywin.example.yaml

@@ -3,16 +3,18 @@
 version: 1
 gap: 8
 shift_drag: true
+active_layout: focus
 
 overlay:
   enabled: true
   color: "#00AEEF"
   opacity: 90
-  border_width: 3
+  border_width: 10
 
 layouts:
   # The wildcard is used for any monitor without a more specific entry.
-  - monitor: "*"
+  - name: focus
+    monitor: "*"
     zones:
       - name: left
         x: 0
@@ -30,9 +32,19 @@ layouts:
         width: 25
         height: 100
 
+  # Other layouts remain available by name. Change active_layout above to
+  # switch layouts; a running FancyWin instance reloads the change.
+  - name: equal-thirds
+    monitor: "*"
+    zones:
+      - { name: left, x: 0, y: 0, width: 33.333, height: 100 }
+      - { name: middle, x: 33.333, y: 0, width: 33.334, height: 100 }
+      - { name: right, x: 66.667, y: 0, width: 33.333, height: 100 }
+
   # Optional per-display override. Get the name from Windows Display Settings
   # or the startup diagnostics, then uncomment and edit this block.
-  # - monitor: '\\.\DISPLAY2'
+  # - name: focus
+  #   monitor: '\\.\DISPLAY2'
   #   zones:
   #     - { name: main, x: 0, y: 0, width: 70, height: 100 }
   #     - { name: side, x: 70, y: 0, width: 30, height: 100 }