refactor: rename loader/model packages to loaders/models

- Rename docforge.loader → docforge.loaders and docforge.model → docforge.models
- Update all imports, type stubs, CLI, tests, and documentation references
- Align MkDocs navigation and docforge.nav.yml with new package structure
- Adjust module docstrings and comments for consistency with pluralized naming

docforge/renderers/mkdocs.py

@@ -5,7 +5,7 @@ compatible with the MkDocs 'material' theme and 'mkdocstrings' extension.
 
 from pathlib import Path
 
-from docforge.model import Project
+from docforge.models import Project
 
 
 class MkDocsRenderer:
@@ -19,10 +19,10 @@ class MkDocsRenderer:
     def generate_sources(self, project: Project, out_dir: Path) -> None:
         """
         Produce a set of Markdown files in the output directory based on the
-        provided Project model.
+        provided Project models.
 
         Args:
-            project: The project model to render.
+            project: The project models to render.
             out_dir: Target directory for documentation files.
         """
         modules = list(project.get_all_modules())