Centralize weather event and driver identifiers

internal/normalizers/spc/convective_outlook_test.go

@@ -32,7 +32,7 @@ func TestConvectiveOutlookNormalizerProducesCanonicalSchemaAndMapsSample(t *test
 	if out.Schema != standards.SchemaWeatherOutlookV1 {
 		t.Fatalf("Schema = %q, want %q", out.Schema, standards.SchemaWeatherOutlookV1)
 	}
-	if out.Kind != event.Kind("outlook") {
+	if out.Kind != event.Kind(standards.KindOutlook) {
 		t.Fatalf("Kind = %q, want outlook", out.Kind)
 	}
 
@@ -276,7 +276,7 @@ func spcRawEvent(t *testing.T, bundle spcprovider.RawConvectiveOutlookBundle) ev
 	effectiveAt := time.Date(2026, 6, 11, 19, 45, 0, 0, time.UTC)
 	return event.Event{
 		ID:          "evt-spc-outlook-1",
-		Kind:        event.Kind("outlook"),
+		Kind:        event.Kind(standards.KindOutlook),
 		Source:      "spc-test",
 		EmittedAt:   time.Date(2026, 6, 11, 20, 5, 0, 0, time.UTC),
 		EffectiveAt: &effectiveAt,