Add omarchy-mac-boot for aarch64 edge

The Apple Silicon boot package (Mac initramfs, in-place encryption, first
boot and the Limine activation gate) now builds from packages/omarchy-mac/boot
in omacom/omarchy-mac at a pinned commit: the recipe runs the source's tests
and install staging, and keeps only metadata, backup= and the pacman
scriptlet from the fork recipe. aarch64 and edge only; 20260925-1 upgrades
the fork's 20260921-10. It needs the Apple-gated limine-mkinitcpio-hook
1.39.0-2.

pkgbuilds/omarchy-mac-boot/omarchy-mac-boot.install

@@ -0,0 +1,48 @@
+_omarchy_mac_boot_asahi_pacsave_notice() {
+  local pacsave=/etc/mkinitcpio.conf.d/90-omarchy-asahi.conf.pacsave
+  local shipped=/etc/mkinitcpio.conf.d/90-omarchy-mac.conf
+
+  [[ -f $pacsave && -f $shipped ]] || return 0
+  cmp -s "$pacsave" "$shipped" && return 0
+
+  cat <<EOF
+==> omarchy-mac-boot: a customized 90-omarchy-asahi.conf was preserved as:
+      $pacsave
+    The active mkinitcpio drop-in is now:
+      $shipped
+    Merge any remaining local changes into the new file.
+EOF
+}
+
+_omarchy_mac_boot_migrate_legacy_first_boot() {
+  local legacy=/var/lib/omarchy/first-boot/pending
+  local successor=/var/lib/omarchy/mac-first-boot/pending
+
+  [[ -e $legacy ]] || return 0
+  install -Dm644 /dev/null "$successor"
+  rm -f "$legacy"
+  systemctl --no-reload enable omarchy-mac-first-boot.service 2>/dev/null || {
+    install -d /etc/systemd/system/multi-user.target.wants
+    ln -sfr /usr/lib/systemd/system/omarchy-mac-first-boot.service \
+      /etc/systemd/system/multi-user.target.wants/omarchy-mac-first-boot.service
+  }
+}
+
+post_install() {
+  _omarchy_mac_boot_asahi_pacsave_notice
+  _omarchy_mac_boot_migrate_legacy_first_boot
+  _omarchy_mac_boot_drop_legacy_wants
+}
+
+_omarchy_mac_boot_drop_legacy_wants() {
+  # The replaced omarchy-first-boot left its preset-enabled link behind.
+  local link=/etc/systemd/system/multi-user.target.wants/omarchy-first-boot.service
+  [[ -L $link && ! -e $link ]] && rm -f "$link"
+  return 0
+}
+
+post_upgrade() {
+  _omarchy_mac_boot_asahi_pacsave_notice
+  _omarchy_mac_boot_migrate_legacy_first_boot
+  _omarchy_mac_boot_drop_legacy_wants
+}