allow overriding matugen type in custom themes

docs/CUSTOM_THEMES.md

@@ -30,7 +30,8 @@ These are the essential colors that define your theme's appearance:
     "surfaceContainerHigh": "#264026",
     "error": "#FF0066",
     "warning": "#CCFF00",
-    "info": "#00FFCC"
+    "info": "#00FFCC",
+    "matugen_type": "scheme-expressive"
   },
   "light": {
     "name": "Cyberpunk Electric Light",
@@ -50,7 +51,8 @@ These are the essential colors that define your theme's appearance:
     "surfaceContainerHigh": "#EBFFEB",
     "error": "#B3004D",
     "warning": "#99CC00",
-    "info": "#00B899"
+    "info": "#00B899",
+    "matugen_type": "scheme-expressive"
   }
 }
 ```
@@ -119,6 +121,25 @@ While the core colors above are required, you can also customize these optional
 - `warning` - Used for warning states and caution indicators
 - `info` - Used for informational states and neutral indicators
 
+### Matugen Color Scheme Type
+```json
+{
+  "matugen_type": "scheme-monochrome"
+}
+```
+
+- `matugen_type` - Controls the color scheme algorithm used by matugen for system app theming
+- **Default**: `scheme-tonal-spot` (if not specified)
+- **Available options**:
+  - `scheme-content` - Content-based color extraction
+  - `scheme-expressive` - Expressive, vibrant color schemes
+  - `scheme-fidelity` - High fidelity to source material
+  - `scheme-fruit-salad` - Colorful, fruit salad-like schemes
+  - `scheme-monochrome` - Monochromatic color schemes
+  - `scheme-neutral` - Neutral, subdued color schemes
+  - `scheme-rainbow` - Rainbow-like color schemes
+  - `scheme-tonal-spot` - Tonal spot color schemes (default)
+
 ## Setting Custom Theme
 
 In settings -> Theme & Colors you can choose "Custom" to choose a path to your theme.