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.

vendor/snapper/scripts/snapper-post.sh

@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+
+# snapper-post.sh
+# ----------------
+# Creates a POST snapshot after a DNF5 transaction completes.
+#
+# This script:
+# - Retrieves stored PRE snapshot and description
+# - Improves description using GUI package info (if available)
+# - Applies SQLite WAL checkpoint fix for libdnf5
+# - Creates the POST snapshot linked to the PRE snapshot
+# - Cleans up temporary state files
+#
+# The WAL checkpoint is necessary on Fedora 44+ to reduce
+# inconsistencies between filesystem state and RPM database.
+#
+# Project: sysguides-snapper-fedora
+# Author: Madhu Desai (SysGuides)
+# Website: https://sysguides.com
+# GitHub: https://github.com/SysGuides/sysguides-snapper-fedora
+
+PID="$1"
+STATE_DIR="/run/snapper-actions"
+
+DESC_FILE="$STATE_DIR/snapper_desc_${PID}"
+PRE_FILE="$STATE_DIR/snapper_pre_${PID}"
+GUI_FILE="$STATE_DIR/snapper_gui_${PID}"
+
+# Load stored state (if available)
+desc=$(cat "$DESC_FILE" 2>/dev/null || echo "")
+pre=$(cat "$PRE_FILE" 2>/dev/null || echo "")
+gui_pkg=$(cat "$GUI_FILE" 2>/dev/null || echo "")
+
+# If no PRE snapshot exists, nothing to do
+[[ -z "$pre" ]] && exit 0
+
+# If GUI package info exists, improve snapshot description
+if [[ -n "$gui_pkg" ]]; then
+    desc="$gui_pkg"
+    snapper -c root modify -d "$desc" "$pre" || true
+fi
+
+# Apply WAL checkpoint (best-effort; do not fail if it doesn't succeed)
+/usr/local/bin/snapper-wal-checkpoint.sh || true
+
+# Create POST snapshot linked to PRE snapshot
+snapper -c root create -c number -t post \
+    --pre-number "$pre" -d "$desc"
+
+# Clean up temporary state files
+rm -f "$DESC_FILE" "$PRE_FILE" "$GUI_FILE"