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/base.py

@@ -7,7 +7,7 @@ DocRenderer protocol.
 from pathlib import Path
 from typing import Protocol
 
-from docforge.model import Project
+from docforge.models import Project
 
 
 class RendererConfig:
@@ -16,7 +16,7 @@ class RendererConfig:
 
     Args:
         out_dir: The directory where documentation files should be written.
-        project: The introspected project model to be rendered.
+        project: The introspected project models to be rendered.
     """
 
     def __init__(self, out_dir: Path, project: Project) -> None:
@@ -40,7 +40,7 @@ class DocRenderer(Protocol):
         Generate renderer-specific source files for the given project.
 
         Args:
-            project: The project model containing modules and objects.
+            project: The project models containing modules and objects.
             out_dir: Target directory for the generated files.
         """
         ...