Enhance JSON payload decoding to accept both typed and pointer payloads, and add corresponding tests

internal/normalizers/spc/convective_outlook_test.go

@@ -107,6 +107,21 @@ func TestConvectiveOutlookNormalizerProducesCanonicalSchemaAndMapsSample(t *test
 	}
 }
 
+func TestConvectiveOutlookNormalizerAcceptsTypedSourcePayload(t *testing.T) {
+	bundle := spcBundle(t, 38.5, -90.5)
+	in := spcRawEvent(t, bundle)
+	in.Payload = bundle
+
+	out, err := (ConvectiveOutlookNormalizer{}).Normalize(nil, in)
+	if err != nil {
+		t.Fatalf("Normalize() error = %v", err)
+	}
+	run := out.Payload.(model.WeatherOutlookRun)
+	if len(run.Outlooks) != 9 {
+		t.Fatalf("Outlooks length = %d, want 9", len(run.Outlooks))
+	}
+}
+
 func TestConvectiveOutlookNormalizerOrdersProductsByDayAndType(t *testing.T) {
 	bundle := spcBundle(t, 0, 0)
 	for i, j := 0, len(bundle.Products)-1; i < j; i, j = i+1, j-1 {