docs: adopt a text-first static layout

docs/book.toml

@@ -11,6 +11,8 @@ build-dir = "../target/docs"
 create-missing = false
 
 [output.html]
-default-theme = "light"
+default-theme = "navy"
+preferred-dark-theme = "navy"
+additional-css = ["theme/lore.css"]
 fold = { enable = false }
 search = { enable = false }