Rebuild the docs around tested examples; shrink README.v2.md to a pitch (#2978)

docs_src/protocol_versions/tutorial001.py

@@ -0,0 +1,15 @@
+from mcp import Client
+from mcp.server import MCPServer
+
+mcp = MCPServer("Bookshop")
+
+
+@mcp.tool()
+def search_books(query: str) -> str:
+    """Search the catalog by title or author."""
+    return f"Found 3 books matching {query!r}."
+
+
+async def main() -> None:
+    async with Client(mcp) as client:
+        print(client.protocol_version)