ports-mgmt/pkg: update to 2.8.1

Changes:

• fix: non-root reads of a WAL-mode database with missing sidecars
• fix: leftover parent @dir directories on deinstall
• fix: static build with -pie
• macho: map macOS 26 / iOS 19 to Darwin 25
• api: add PKG_EVENT_PKG_FETCH_BEGIN for per-package fetch progress
• fix: missing space in a libpkg error message