Move full-runtime dep to omarchy meta; thin omarchy-installer

Apollo-recommended dep split:
- omarchy-installer: bash gum jq git only (just the runner)
- omarchy: depends on omarchy-keyring + omarchy-settings + omarchy-limine
  + the runtime stack
- omarchy-settings, omarchy-limine: standalone

install.sh now installs the runtime (pacman -Syu --needed omarchy) before
sourcing preflight/all.sh in online mode, and asserts it's already
present in offline mode (ISO pacstraps it before user creation so
/etc/skel is populated).

boot.sh installs only omarchy-keyring + omarchy-installer (small + fast),
then exec's omarchy-install which handles the full-runtime pull.

User-visible effect: 'pacman -S omarchy-installer' now installs ~5 files
instead of the entire Omarchy stack. Users get a clean choice between
'I just want the installer' and 'I want the full Omarchy desktop'.

boot.sh

@@ -45,7 +45,9 @@ echo "Refreshing pacman databases..."
 sudo pacman -Sy --noconfirm
 
 echo "Installing omarchy-installer..."
-sudo pacman -S --noconfirm --needed omarchy-installer
+# Only install the runner here — install.sh pulls the full omarchy runtime
+# itself once it knows the mode and has logged in.
+sudo pacman -S --noconfirm --needed omarchy-keyring omarchy-installer
 
 echo -e "\nInstallation starting..."
 exec omarchy-install