fix(mackup): update backup path and enhance configuration handling

- Corrected the backup path in the `_in_backup` function to reflect the new structure under `mackup/`.
- Improved error handling in `ssr::mackup::configure` to skip restore if the configuration file is not updated, providing user feedback.
- Updated `ssr::sync` to conditionally execute backup based on configuration validity, enhancing robustness.
- Revised documentation in configuration examples to clarify the new Mackup directory structure and its implications for users.

config/post-restore.sh.example

@@ -13,7 +13,7 @@
 # Available variables:
 #   SSR_ROOT       — path to the ssr repository
 #   backup_dir     — cloud backup directory for this host
-#   mackup_dir     — cloud Mackup directory
+#   mackup_dir     — cloud path parent for Mackup (~/.mackup.cfg path=…; files under …/mackup/)
 #
 # EXAMPLES
 # -------------------------------------------------------------------------

config/ssr.conf.example

@@ -12,14 +12,18 @@ SSR_CLOUD_PROVIDER=icloud
 # Only used when SSR_CLOUD_PROVIDER=custom. Absolute path.
 # SSR_CLOUD_PATH=/Volumes/MyNAS/macos-sync
 
-# Subfolders created inside the cloud root.
+# Subfolder inside the cloud root for SSR data: per-host backups live under
+# <cloud>/<SSR_BACKUP_SUBDIR>/<hostname> - <uuid>/. Mackup storage uses the
+# same parent path; ~/.mackup.cfg sets directory=mackup (see ssr::mackup::configure).
 SSR_BACKUP_SUBDIR=BACKUP
-SSR_MACKUP_SUBDIR=Mackup
 
 # SSR uses `mackup backup` / `mackup restore` (copy, not symlinks) for reliability
 # on newer macOS. If you still have Mackup symlinks from an older setup, run:
 #   ssr mackup unlink
 
+# SSR_ALLOW_CONF_OVERWRITE=yes  — apply ~/.mackup.cfg updates without a TTY prompt
+# (launchd / CI). Interactive runs show a diff and ask before replacing.
+
 # Subdirs (relative to $HOME) to delete before each mackup backup attempt.
 # Handles transient dirs with dangling symlinks or sockets (debug sessions,
 # log dirs) that should not be copied to cloud.