Fix boot-critical, session, and UX bugs found in round-3 UX audit

Snapshots panel was non-functional (wrong snapper flag); breadgreet picked
the wrong session .desktop and skipped bos-session's PATH fixup; Calamares
aborted offline installs over an unnecessary packages module; snapshot
rollback silently no-op'd on BOS's pinned-subvolume layout (now points at
grub-btrfs instead); breadcrumbs was configurable but had no daemon to run
it. Also: SUPER+I double-bind, breadpaper/packages panels blocking the GTK
main thread, dead polkit rule, and a sweep of smaller drift (default
sidebar view, stale wording, missing .desktop launchers, wallpaper daemon
not recording its own default).

iso/airootfs/etc/os-release

@@ -9,4 +9,3 @@ DOCUMENTATION_URL="https://wiki.archlinux.org/"
 SUPPORT_URL="https://bbs.archlinux.org/"
 BUG_REPORT_URL="https://git.breadway.dev/Breadway/bos/issues"
 PRIVACY_POLICY_URL="https://terms.archlinux.org/docs/privacy-policy/"
-LOGO=archlinux-logo