feat(wm): add layout_options with ratios support

Added customizable split ratios for layouts via layout_options
configuration. Users can now specify column_ratios and row_ratios arrays
to control window sizing in various layouts.

Ratios are validated at config load time: values are clamped between 0.1
and 0.9 to prevent zero-sized windows, and arrays are automatically
truncated when their cumulative sum would reach or exceed 1.0. This
ensures there's always remaining space for additional windows.

Ratio support varies by layout:

- Columns and Rows layouts use the full arrays for each column/row width
  or height
- VerticalStack, RightMainVerticalStack, and HorizontalStack use the
  first ratio for the primary split and the remaining ratios for stack
  windows
- BSP uses the first value from each array for horizontal and vertical
  splits respectively
- Grid only supports column_ratios since row counts vary dynamically.
- UltrawideVerticalStack uses the first two column ratios for center and
  left columns.

All ratio-related values are now defined as constants in
default_layout.rs: MAX_RATIOS (5), MIN_RATIO (0.1), MAX_RATIO (0.9),
DEFAULT_RATIO (0.5), and DEFAULT_SECONDARY_RATIO (0.25 for
UltrawideVerticalStack).

schema.bar.json

@@ -59,7 +59,7 @@
         "null"
       ],
       "format": "float",
-      "default": 50.0
+      "default": 50
     },
     "icon_scale": {
       "description": "Scale of the icons relative to the font_size [[1.0-2.0]]",
@@ -68,7 +68,7 @@
         "null"
       ],
       "format": "float",
-      "default": 1.399999976158142
+      "default": 1.4
     },
     "left_widgets": {
       "description": "Left side widgets (ordered left-to-right)",
@@ -99,7 +99,15 @@
     },
     "monitor": {
       "description": "The monitor index or the full monitor options",
-      "$ref": "#/$defs/MonitorConfigOrIndex"
+      "anyOf": [
+        {
+          "$ref": "#/$defs/MonitorConfigOrIndex"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": 0
     },
     "mouse": {
       "description": "Options for mouse interaction on the bar",
@@ -174,7 +182,6 @@
     }
   },
   "required": [
-    "monitor",
     "left_widgets",
     "right_widgets"
   ],