feat: rework entry pages and setup guides

tests/test_contributing_text.py

@@ -22,7 +22,7 @@ import generate_site  # noqa: E402
 def _normalized(text: str) -> str:
     # The site ends each page with its next step in the reading order. That
     # is navigation, not contributing text, and a repository file has none.
-    text = text.split("\n\n:::tip[Next]\n", 1)[0].rstrip("\n")
+    text = text.split("\n## Next steps\n", 1)[0].rstrip("\n")
     text = re.sub(r"\]\([^)]*\)", "](link)", text)
     return "\n".join(text.splitlines()[1:]).replace("on this site", "on the documentation site")