Migrate ordinary I/O from confined file helpers

internal/artifacts/prepared_input.go

@@ -6,11 +6,11 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"os"
 	"path/filepath"
 	"strings"
 
 	"gitea.maximumdirect.net/eric/narratio/internal/artifactpolicy"
-	"gitea.maximumdirect.net/eric/narratio/internal/fileops"
 	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
 )
 
@@ -107,11 +107,16 @@ func ResolvePreparedInput(paths SessionPaths, m *manifest.Manifest, sourceID str
 		return PreparedInputIdentity{}, fmt.Errorf("prepared input source %q manifest checksum is required", descriptor.SourceID)
 	}
 
-	file, err := fileops.OpenConfinedRegularFile(rootPath, relativePath)
+	file, err := os.Open(filepath.Join(rootPath, filepath.FromSlash(relativePath)))
 	if err != nil {
 		return PreparedInputIdentity{}, fmt.Errorf("open prepared input source %q: %w", descriptor.SourceID, err)
 	}
 	digest := sha256.New()
+	info, statErr := file.Stat()
+	if statErr != nil || !info.Mode().IsRegular() {
+		_ = file.Close()
+		return PreparedInputIdentity{}, fmt.Errorf("prepared input source %q is not a regular file", descriptor.SourceID)
+	}
 	size, readErr := io.Copy(digest, file)
 	closeErr := file.Close()
 	if readErr != nil {