feat(metadata): enhance metadata handling by sanitizing extracted data and updating documentation for file storage

internal/metadata/normalize.go

@@ -110,6 +110,15 @@ func MarkMetadataComplete(base thoughttypes.ThoughtMetadata, capture config.Capt
 	return out
 }
 
+func SanitizeExtracted(in thoughttypes.ThoughtMetadata) thoughttypes.ThoughtMetadata {
+	in.Attachments = nil
+	in.MetadataStatus = ""
+	in.MetadataUpdatedAt = ""
+	in.MetadataLastAttemptedAt = ""
+	in.MetadataError = ""
+	return in
+}
+
 func normalizeList(values []string, limit int) []string {
 	seen := make(map[string]struct{}, len(values))
 	result := make([]string, 0, len(values))