fix: Add CachyOS test VM dev environment and VM testing skill

QEMU/KVM scripts for a CachyOS KDE test VM (run.sh/run.ps1, get-iso,
guest SSH setup), host helper scripts to drive and inspect the
cachyos-gamescope-boot wizard in the guest, and a Claude Code skill
documenting the test workflow.

scripts/cmp.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+# Diff the guest's KDE/GTK configs against a saved baseline.
+#   scripts/cmp.sh save   copy the current ~/.config files to the baseline
+#   scripts/cmp.sh        show differences against the baseline
+# Env: VM_USER (theupriser), VM_PORT (2222), VM_HOST (localhost),
+#      BASELINE (guest dir, default ~/.cache/vm-baseline; not /tmp, which is cleared on reboot).
+set -euo pipefail
+. "$(dirname "$0")/common.sh"
+mode="${1:-diff}"
+# The guest login shell is fish, so pass values in through the bash script itself.
+{ printf 'mode=%q base=%q\n' "$mode" "${BASELINE:-}"; cat << 'REMOTE'
+base="${base:-$HOME/.cache/vm-baseline}"
+files="kdeglobals plasmarc plasmashellrc kwinrc kwinrulesrc konsolerc kscreenlockerrc kglobalshortcutsrc gtk-3.0/settings.ini gtk-4.0/settings.ini plasma-org.kde.plasma.desktop-appletsrc"
+if [ "$mode" = save ]; then
+  for f in $files; do mkdir -p "$(dirname "$base/config/$f")"; cp -f ~/.config/"$f" "$base/config/$f" 2>/dev/null || true; done
+  echo "baseline saved to $base"; exit 0
+fi
+noise='^(ColorSchemeHash|popupHeight|popupWidth|ItemGeometries|ItemGeometriesHorizontal|DialogHeight|DialogWidth|[0-9]+ screens: )'
+for f in $files; do
+  d=$(diff <(sort -u "$base/config/$f" 2>/dev/null | grep -vE "$noise") <(sort -u ~/.config/"$f" 2>/dev/null | grep -vE "$noise") | grep '^[<>]' || true)
+  [ -n "$d" ] && { echo "== $f"; echo "$d" | head -25; }
+done
+echo "(end of diff)"
+REMOTE
+} | vm_ssh bash -s 2>&1