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

docs_src/session_groups/tutorial001.py

@@ -0,0 +1,15 @@
+from mcp.server import MCPServer
+
+mcp = MCPServer("Library")
+
+
+@mcp.tool()
+def search(query: str) -> str:
+    """Search the library catalog."""
+    return f"3 books match {query!r}."
+
+
+@mcp.resource("library://hours")
+def hours() -> str:
+    """When the library is open."""
+    return "Mon-Fri 09:00-17:00"