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

docs_src/asgi/tutorial006.py

@@ -0,0 +1,20 @@
+from starlette.requests import Request
+from starlette.responses import JSONResponse, Response
+
+from mcp.server import MCPServer
+
+mcp = MCPServer("Notes")
+
+
+@mcp.tool()
+def add_note(text: str) -> str:
+    """Save a note."""
+    return f"Saved: {text}"
+
+
+@mcp.custom_route("/health", methods=["GET"])
+async def health(request: Request) -> Response:
+    return JSONResponse({"status": "ok"})
+
+
+app = mcp.streamable_http_app()