Add omarchycn update for overlay installs with migration runner

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QKxGW1raAWaqeU8WdHsMsp

bin/omarchy-cn-update

@@ -0,0 +1,47 @@
+#!/bin/bash
+# omarchy:summary=Update an overlay install: pull source, reinstall, run migrations
+# omarchy:examples=omarchycn update
+
+set -euo pipefail
+
+MANIFEST="$HOME/.local/state/omarchycn/overlay-manifest"
+MIGRATION_STATE="$HOME/.local/state/omarchycn/last-migration"
+
+if [[ ! -f $MANIFEST ]]; then
+  echo "Not an overlay install (no $MANIFEST)." >&2
+  echo "Package-based installs update through 'omarchy update' / pacman." >&2
+  exit 1
+fi
+
+src=$(grep -m1 '^source=' "$MANIFEST" | cut -d= -f2-)
+if [[ ! -d $src/.git ]]; then
+  echo "Overlay source $src is not a git checkout" >&2
+  exit 1
+fi
+
+old=$(git -C "$src" rev-parse --short HEAD)
+git -C "$src" pull --ff-only
+new=$(git -C "$src" rev-parse --short HEAD)
+echo "Source: $old -> $new"
+
+"$src/bin/omarchy-cn-install-overlay"
+
+# Run migrations newer than the last recorded one, in filename order
+last=""
+if [[ -f $MIGRATION_STATE ]]; then
+  last=$(<"$MIGRATION_STATE")
+fi
+
+if [[ -d $src/cn/migrations ]]; then
+  for m in "$src"/cn/migrations/*.sh; do
+    [[ -f $m ]] || continue
+    name="${m##*/}"
+    if [[ $name > $last ]]; then
+      echo "Migration: $name"
+      bash "$m"
+      echo "$name" > "$MIGRATION_STATE"
+    fi
+  done
+fi
+
+echo "OmarchyCN update complete ($(omarchy-cn-version 2>/dev/null || echo unknown))"