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).

bos-settings/src/ui/views/breadcrumbs.rs

@@ -356,7 +356,9 @@ pub fn build() -> GBox {
         &doc,
         &["settings", "default_profile"],
         &["home", "away"],
-        "home",
+        // breadcrumbs' own default_profile_name() is "away", not "home" —
+        // this was showing the wrong value for an unset key.
+        "away",
     ));
     content.append(&w::entry_row("DNS", &doc, &["settings", "dns"], "1.1.1.1", ""));
     content.append(&w::entry_row(