Remove the completed step 4 migration roadmap

internal/adapter/http/artifact_reader_test.go

@@ -3,6 +3,7 @@ package httpadapter
 import (
 	"context"
 	"errors"
+	"mime"
 	"os"
 	"path/filepath"
 	"testing"
@@ -26,6 +27,10 @@ func TestRestrictedArtifactReaderReadsContainedFiles(t *testing.T) {
 	if err := os.WriteFile(filepath.Join(outside, "secret.txt"), []byte("denied"), 0o644); err != nil {
 		t.Fatal(err)
 	}
+	expectedContentType := mime.TypeByExtension(filepath.Ext(inputPath))
+	if expectedContentType == "" {
+		t.Fatal("expected built-in HTML content type")
+	}
 
 	reader, err := NewRestrictedArtifactReader(root, 0)
 	if err != nil {
@@ -43,8 +48,8 @@ func TestRestrictedArtifactReaderReadsContainedFiles(t *testing.T) {
 		if artifact.Name != "input.html" || artifact.URI != inputPath || artifact.Size != int64(len("allowed")) || string(artifact.Body) != "allowed" {
 			t.Fatalf("unexpected artifact metadata: %#v", artifact)
 		}
-		if artifact.ContentType != "text/html; charset=utf-8" {
-			t.Fatalf("unexpected artifact content type: %q", artifact.ContentType)
+		if artifact.ContentType != expectedContentType {
+			t.Fatalf("unexpected artifact content type: got %q, want %q", artifact.ContentType, expectedContentType)
 		}
 		if artifact.Hash != artifactHash([]byte("allowed")) {
 			t.Fatalf("unexpected artifact hash: %q", artifact.Hash)