v1.2.0 - People: leadership and board

Adds the ans_people_group taxonomy (leadership / board) to the existing person CPT, per-person meta (pronouns, occupation, job title, display order, board office, term) with an admin meta box, and the [ans_people group=...] shortcode that drives the public Leadership page. Deliberately separate from the Singers Portal: never reads or writes the portal ans_group permissions taxonomy, and never touches the singer CPT. Installable zip attached (top folder ars-nova-core/).