Change: Update recipe generation to use single universal template

- Transition from multi-template (install/live recipe types) to single universal template (proteus)
- Remove recipe_type parameter from RecipeGenerator
- Update manifest format (remove recipe_type field)
- Simplify CLI (remove --type argument, use --output for single generation)
- Filename generation now uses primary modifier as first component

cook/generate_recipe.py

@@ -5,8 +5,11 @@ the recipe generator. It follows the common Python pattern of having a script
 that can be run directly or imported as a module.
 
 Usage:
-    # Run as script
-    python generate_recipe.py --type virtual-desktop --version 43 --output output.cfg
+    # Run as script for single generation
+    python generate_recipe.py --output my-recipe.cfg --version 43 --desktop gnome
+    
+    # Or using the universal template with modifiers
+    python generate_recipe.py --output single.cfg --version 43 --guest-agents true
     
     # Or from another Python script
     from generate_recipe import main