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

docs_src/client_transports/tutorial004.py

@@ -0,0 +1,14 @@
+from mcp import Client, StdioServerParameters
+from mcp.client.stdio import stdio_client
+
+server = StdioServerParameters(
+    command="uv",
+    args=["run", "server.py"],
+    env={"BOOKSHOP_API_KEY": "secret"},
+)
+
+
+async def main() -> None:
+    async with Client(stdio_client(server)) as client:
+        result = await client.list_tools()
+        print([tool.name for tool in result.tools])