CVE-2026-14669: reject POSIX timezone abbreviations longer than the
to_char() format workspace budget (n->key->len * DCH_MAX_ITEM_SIZ) in
DCH_to_char()'s TZ/tz items instead of strcpy()ing them past the end
of the palloc'd buffer (heap overflow, CVSS 8.8; security hunk of
upstream REL_14_STABLE 5fb3c63, shipped in 14.24)