docs(readme): UCP example uses payment.mpp shape

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: vvillait88

README.md

@@ -232,13 +232,13 @@ profile = build_ucp_profile(
         ],
     },
     payment_handlers={
-        "sh.agentscore.payment.tempo": [
+        "sh.agentscore.payment.mpp": [
             UCPPaymentHandlerBinding(
-                id="tempo",
+                id="mpp",
                 version="2026-04-08",
-                spec="https://agentscore.sh/specification/payment-handlers/tempo",
-                schema="https://agentscore.sh/schemas/payment-handlers/tempo.json",
-                config={"recipient": TEMPO_ADDR},
+                spec="https://agentscore.sh/specification/payment-handlers/mpp",
+                schema="https://agentscore.sh/schemas/payment-handlers/mpp.json",
+                config={"chains": {"tempo": {"rail": "tempo-mainnet", "chain_id": 4217}}},
             ),
         ],
     },