Use main for the main provenance layer

internal/engine/metadata_test.go

@@ -146,7 +146,7 @@ func TestHistoricalPathsExposeHiddenBaseOwnershipWithoutResolvingBaseSecrets(t *
 				found = true
 				owners := map[string]bool{}
 				for _, change := range metadata.History(path) {
-					if change.Origin.Layer == LayerBase {
+					if change.Origin.Layer == LayerMain {
 						for _, location := range change.Origin.Locations {
 							owners[location.SourceID] = true
 						}
@@ -188,7 +188,7 @@ func TestMetadataQueriesReturnDetachedRecords(t *testing.T) {
 			path.String(): {
 				Explicit: true,
 				Origin: Origin{
-					Layer:     LayerBase,
+					Layer:     LayerMain,
 					Locations: []Location{{SourceID: "source-1", Line: 2, Column: 3}},
 				},
 			},
@@ -246,7 +246,7 @@ func TestResolutionInputKeepsDetachedEntryMetadata(t *testing.T) {
 	}
 	metadata := metadataFromDecoded(decoded)
 	input := newResolutionInput(metadata, decoded.final, []SourceInfo{{
-		ID: "source-1", Label: "decode.yml", Layer: LayerBase,
+		ID: "source-1", Label: "decode.yml", Layer: LayerMain,
 		ImportedFrom: &Location{SourceID: "parent", Line: 1, Column: 1},
 	}})