feat: add --api OpenAPI build mode with docs/api scheme and lib-prefixed nav

docforge/templates/mkdocs.lib.yml

@@ -0,0 +1,19 @@
+plugins:
+  - search
+  - mkdocstrings:
+      handlers:
+        python:
+          paths: ["."]
+          options:
+            docstring_style: google
+            show_source: false
+            show_signature_annotations: true
+            separate_signature: true
+            merge_init_into_class: true
+            inherited_members: true
+            annotations_path: brief
+            show_root_heading: true
+            group_by_category: true
+            show_category_heading: true
+            show_object_full_path: false
+            show_symbol_type_heading: true