Add moonarch-update for package-based system maintenance

Simplified updater that reads package lists from /usr/share/moonarch/
instead of syncing a git repo. Designed to be shipped by the
moonarch-git package as /usr/bin/moonarch-update.

DECISIONS.md

@@ -11,3 +11,9 @@
 - **Why**: Users with existing Arch+Wayland setups should be able to adopt Moonarch without reinstalling
 - **Tradeoffs**: Hard overwrite of all configs (user + system) vs. selective/merge approach — chose hard overwrite for simplicity and consistency
 - **How**: New transform.sh with pre-flight summary, backup, DM conflict resolution, and --dry-run flag. Shared helpers extracted to lib.sh.
+
+## 2026-03-29 – Package moonarch as moonarch-git PKGBUILD
+- **Who**: Dominik, Ragnar
+- **Why**: System artifacts (XDG configs, helper scripts, zsh config, wallpaper) should be managed by pacman for clean deployment, versioning, rollback, and deinstallation
+- **Tradeoffs**: /etc/xdg/ configs NOT in backup= (moonarch philosophy: system defaults flow through, users override in ~/.config/). /etc/greetd/ and /etc/moongreet/ NOT owned by package (owned by greetd/moongreet-git, overwritten via .install hook). Helper scripts move from /usr/local/bin/ to /usr/bin/ (FHS for package-managed files)
+- **How**: moonarch-git PKGBUILD in moonarch-pkgbuilds repo. sweet-cursors-git as separate package. moonarch-update simplified (no git-sync, pacman handles file deployment). Installer scripts (post-install.sh, transform.sh) remain for orchestration, will be refactored in a follow-up to delegate file deployment to `paru -S moonarch-git`