Snapper: no question on btrfs; vendor the SysGuides scripts

- On btrfs, snapshots + zstd compression now just happen (no prompt);
  --snapper=no remains the explicit opt-out.
- Vendor scripts/snapper-*.sh + config/snapper.actions from
  SysGuides/sysguides-snapper-fedora (MIT, upstream 0a28eb4) into
  vendor/snapper/ and install from there — no runtime clone of an
  external repo, and no dependency on exec bits (fixes the
  './install.sh: Permission denied' failure seen on the test VM).
- grub-btrfs still cloned at runtime from Antynea/grub-btrfs with the
  Fedora config applied; everything else is local now.

setup.sh

@@ -36,7 +36,7 @@ Options:
   --de=NAME     gnome | plasma | xfce | none
   --twm=NAME    chadwm | hyprland | mango | niri | none
   --selinux=X   keep | disabled   (asked, default keep)
-  --snapper=X   yes | no          (asked when / is btrfs, default yes)
+  --snapper=X   yes | no          (automatic on btrfs; use 'no' to opt out)
   --dotfiles=X  yes | no          (clone personal dotfiles, default no)
   -y, --yes     never prompt (requires --de and --twm)
   -d, --debug   pause after each section instead of aborting on error
@@ -244,9 +244,8 @@ if [[ -z "$SELINUX_OPT" ]]; then
     [[ "$choice" == "yes" ]] && SELINUX_DISABLED=true
     printf "\n"
     if findmnt -n -o FSTYPE / 2>/dev/null | grep -q btrfs; then
-        ok "Root filesystem is btrfs — snapshot support is available."
-        choice=$(ask_yes_no "Set up snapper + grub-btrfs snapshots and zstd compression?" "yes")
-        [[ "$choice" == "yes" ]] && BTRFS_SNAPPER=true
+        ok "Root filesystem is btrfs — snapshots + zstd compression will be set up."
+        BTRFS_SNAPPER=true
     else
         info "Root filesystem is not btrfs; skipping snapshot setup."
     fi