Consumer access to custom/error records

FTA is a good example. The consumer needs to be able to access the lines tied to records which YAGP is marking as unknown.

The consumer needs to be able to list those records, see the GEDCOM text lines associated, and ideally access those lines pre-split into level/tag/remainder.

This would be so a consumer could support a custom tag which YAGP is not handling.

No file or test is named. Start by tracing how YAGP marks records as unknown and how consumers currently access records; then determine the consumer-facing entry point for listing them and retrieving their GEDCOM lines, including level, tag, and remainder parts. Done means a consumer can support an otherwise-unhandled custom tag.

Written by the indexing model from the issue text.