Scaffold Python orchestrator + split install.sh / finalize.sh

Chunk 1 of the C3 refactor: replace the two-pass install model (archinstall
CLI + custom shell dance + chroot bash installer) with a single Python
orchestrator that owns phase ordering, using archinstall as a library
subsystem.

Splits the bash entry point into two:
- install.sh: online entry point. Ensures omarchy runtime + base.packages
  are installed/up to date, then exec's finalize.sh.
- finalize.sh: the in-target portion (preflight + packaging + config +
  login + post-install). Called by install.sh (online) AND by the
  orchestrator after arch-chroot -u $USER (offline).

Adds the orchestrator skeleton under install/orchestrator/:
- main.py: entry point, builds + runs the phase list
- context.py: InstallContext (parsed configurator JSON + invocation paths)
- phases.py: phase state machine (logging + state.json + error wrapping)
- phases_impl.py: stubbed phase implementations (filled in by chunks 2-6)
- archinstall_adapter.py: thin compat wall around archinstall lib imports
  (only this module imports from archinstall.*)
- ui.py: gum subprocess wrappers so the orchestrator keeps the same
  styled-terminal UX as the bash installer

Updates bin/omarchy-install to dispatch:
- --config <json> in args → python -m orchestrator.main (ISO install)
- anything else → bash install.sh (online rerun on installed system)

Concrete phase logic lands in subsequent chunks. All phases currently
raise NotImplementedError; the orchestrator imports cleanly and --help
works as a smoke check.

bin/omarchy-install

@@ -2,6 +2,25 @@
 
 # omarchy:summary=Run the Omarchy installer (shipped via omarchy-installer)
 # omarchy:group=install
-# omarchy:args=[install.sh args]
+# omarchy:args=[--config <json> --creds <json> ...] | [install.sh args]
 
-exec bash "$OMARCHY_PATH/install.sh" "$@"
+set -eEo pipefail
+
+# Dispatcher:
+#   --config <json>  → Python orchestrator (ISO install)
+#   anything else    → bash install.sh (online rerun on an installed system)
+#
+# The Python orchestrator owns the ISO install end-to-end: partitioning,
+# pacstrap, bootloader, user creation, package install, and finally calling
+# finalize.sh inside the chroot. install.sh is the simpler online path:
+# ensures the omarchy runtime is up to date, then exec's finalize.sh.
+for arg in "$@"; do
+  case "$arg" in
+    --config|--config=*)
+      cd "${OMARCHY_PATH:-/usr/share/omarchy}/install"
+      exec python -m orchestrator.main "$@"
+      ;;
+  esac
+done
+
+exec bash "${OMARCHY_PATH:-/usr/share/omarchy}/install.sh" "$@"