Make setup ISO-only

Remove legacy online installer entrypoints, collapse migrations for 4.0, and move setup responsibilities into target-side system, hardware, and user commands.

bin/omarchy-update

@@ -7,8 +7,6 @@
 
 set -e
 
-# Run the update inside a PTY so pacman/yay keep showing download progress
-# while still logging the full session for later analysis.
 if [[ -z $OMARCHY_UPDATE_LOGGED ]]; then
   script_command=$(printf '%q ' "$0" "$@")
   exec env OMARCHY_UPDATE_LOGGED=1 script -qefc "$script_command" "/tmp/omarchy-update.log"
@@ -16,8 +14,7 @@ fi
 
 trap 'echo ""; echo -e "\033[0;31mSomething went wrong during the update!\n\nPlease review the output above carefully, correct the error, and retry the update.\n\nIf you need assistance, get help from the community at https://omarchy.org/discord\033[0m"' ERR
 
-if [[ $1 == "-y" ]] || omarchy-update-confirm; then
+if [[ ${1:-} == "-y" ]] || omarchy-update-confirm; then
   omarchy-snapshot create || (($? == 127))
-  omarchy-update-git
   omarchy-update-perform
 fi