fix: parse MCP result payloads and drop place idempotency_key

Typed result structs replace empty envelopes. Equity place sends
ref_id only so live additionalProperties:false schemas accept the call.

market/market_test.go

@@ -241,3 +241,17 @@ func TestEarningsResults_rhntest(t *testing.T) {
 		t.Fatal(diff)
 	}
 }
+
+func TestEarningsResults_liveEnvelope(t *testing.T) {
+	t.Parallel()
+	c := market.New(client.Func(func(ctx context.Context, name string, args map[string]any) (json.RawMessage, error) {
+		return json.RawMessage(`{"data":{"results":[{"report":{"date":"2026-07-15"}}]}}`), nil
+	}))
+	got, err := c.EarningsResults(context.Background(), market.EarningsResultsRequest{Symbol: "MU"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.ReportDate != "2026-07-15" || got.NextReportDate != "2026-07-15" {
+		t.Fatalf("%+v", got)
+	}
+}