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/greetd/breadgreet.example.toml

@@ -0,0 +1,26 @@
+# breadgreet commonly runs as the dedicated `greeter` system user (per
+# greetd's own convention), so it checks /etc/greetd/breadgreet.toml first;
+# copy this there for a real install. For local dev/testing under a normal
+# user session it falls back to ~/.config/breadgreet/breadgreet.toml.
+#
+# Every field is optional and defaults to the value shown here.
+
+[background]
+mode = "color"
+path = ""
+blur = false
+
+[clock]
+format = "%H:%M"
+
+[font]
+family = "Varela Round"
+
+[sessions]
+# Directories scanned for .desktop session entries, in order.
+wayland_dirs = ["/usr/share/wayland-sessions"]
+xsessions_dirs = ["/usr/share/xsessions"]
+# .desktop file stem (without extension) to auto-select. Falls back to the
+# first entry found if this isn't present. v1 has no session picker UI —
+# BOS only ships one session (Hyprland) today.
+default = "hyprland"

iso/airootfs/etc/greetd/breadgreet.toml

@@ -0,0 +1,15 @@
+# BOS's real breadgreet config — see breadgreet.example.toml in this same
+# directory for the full set of options with explanations.
+#
+# The one setting that actually matters here: `sessions.default` MUST be
+# "bos", not breadgreet's compiled-in default of "hyprland". The `hyprland`
+# pacman package installs its own /usr/share/wayland-sessions/hyprland.desktop
+# alongside BOS's own bos.desktop, and breadgreet's session picker matches by
+# .desktop file stem — with no override it picks "hyprland.desktop" over
+# "bos.desktop", which skips bos-session's PATH fixup (adds ~/.local/bin for
+# the bakery bread apps; greetd starts no login shell, so /etc/profile.d is
+# never sourced any other way). Confirmed via breadgreet's own test suite
+# (sessions.rs: discover_prefers_configured_default_over_first_entry).
+
+[sessions]
+default = "bos"

iso/airootfs/etc/greetd/config.toml

@@ -2,11 +2,15 @@
 # squashfs and enabled by post-install.sh; the live ISO instead autologins
 # liveuser on tty1 (see getty@tty1 drop-in) so the installer comes straight up.
 #
-# tuigreet shows a minimal greeter, then launches the BOS Hyprland session via
-# bos-session (which fixes up PATH for the bakery bread apps).
+# breadgreet (bread-ecosystem's own greeter) is hosted under cage — a single-
+# client kiosk Wayland compositor, since greetd itself has no display of its
+# own — and speaks greetd's IPC directly. It resolves the session to launch
+# from /usr/share/wayland-sessions/bos.desktop, which points at bos-session
+# (fixes up PATH for the bakery bread apps; greetd starts no login shell, so
+# /etc/profile.d is never sourced otherwise).
 [terminal]
 vt = 1
 
 [default_session]
-command = "tuigreet --remember --time --cmd /usr/local/bin/bos-session"
+command = "cage -s -- breadgreet"
 user = "greeter"