fix: preserve original filename when using --front-matter (#2613)

When using --front-matter, yq creates a temporary file for the
extracted YAML content but replaces the original filename in args
with the temp file path. This caused the 'filename' operator to
return the temp file path instead of the original filename.

Added a filename alias mechanism: when front matter processing
replaces the file path, it registers the original filename as an
alias. The readDocuments and stream evaluator functions resolve
aliases before setting candidateNode.filename.

Fixes #2538

Co-authored-by: cobyfrombrooklyn-bot <cobyfrombrooklyn@gmail.com>

cmd/evaluate_sequence_command.go

@@ -122,12 +122,15 @@ func evaluateSequence(cmd *cobra.Command, args []string) (cmdError error) {
 
 	if frontMatter != "" {
 		yqlib.GetLogger().Debug("using front matter handler")
+		originalFilename := args[0]
 		frontMatterHandler := yqlib.NewFrontMatterHandler(args[0])
 		err = frontMatterHandler.Split()
 		if err != nil {
 			return err
 		}
 		args[0] = frontMatterHandler.GetYamlFrontMatterFilename()
+		yqlib.SetFilenameAlias(args[0], originalFilename)
+		defer yqlib.ClearFilenameAliases()
 
 		if frontMatter == "process" {
 			reader := frontMatterHandler.GetContentReader()