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

docs_src/client_callbacks/tutorial002.py

@@ -0,0 +1,21 @@
+from mcp_types import ElicitRequestParams, ElicitResult
+
+from mcp import Client
+from mcp.client import ClientRequestContext
+
+
+async def handle_elicitation(
+    context: ClientRequestContext,
+    params: ElicitRequestParams,
+) -> ElicitResult:
+    return ElicitResult(action="accept", content={"name": "Ada Lovelace"})
+
+
+async def main() -> None:
+    async with Client(
+        "http://127.0.0.1:8000/mcp",
+        mode="legacy",
+        elicitation_callback=handle_elicitation,
+    ) as client:
+        result = await client.call_tool("issue_card")
+        print(result.content)