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.

install/omarchy-base.packages

@@ -1,5 +1,5 @@
-# Omarchy core package list installed via install/packaging/base.sh
-# This file is also used by the ISO builder when determining needs
+# Omarchy core package list pacstrapped by the ISO.
+# The ISO builder also reads this file when constructing the offline mirror.
 
 aether
 alsa-utils