docs: add wiki, complete lib nav, and rebuild mcp artifacts

- Add hand-written wiki (index, overview, how-to, extending, dev) with
  MkDocs config following the platform anatomy
- Complete the library nav by registering the csv and xlsx groups in
  docforge.nav.yml and docs/mkdocs.lib.yml
- Regenerate lib/MCP outputs with the rebuilt nav

docforge.nav.yml

@@ -14,6 +14,18 @@ groups:
     - lib/pdf/client.md
     - lib/pdf/parser.md
     - lib/pdf/scraper.md
+  CSV Handling:
+    - lib/csv/index.md
+    - lib/csv/client.md
+    - lib/csv/parser_base.md
+    - lib/csv/parser.md
+    - lib/csv/scraper.md
+  XLSX Handling:
+    - lib/xlsx/index.md
+    - lib/xlsx/client.md
+    - lib/xlsx/parser_base.md
+    - lib/xlsx/parser.md
+    - lib/xlsx/scraper.md
 icon:
   logo: material/book-open-page-variant
   repo: fontawesome/brands/github