aitools: use $HOME in update-prune test

Address review feedback: sethome exports HOME on Windows too (see
acceptance/script.prepare), so the ${USERPROFILE:-$HOME} fallback is
unnecessary here. Use plain $HOME.

Co-authored-by: Isaac

Author: simonfaltum

acceptance/experimental/aitools/skills/update-prune/script

@@ -5,8 +5,8 @@ sethome home
 # the raw-skill prune path without shelling out to a plugin-capable agent's CLI.
 # A plugin agent (e.g. Claude Code) would run `claude plugin install` during
 # update, making the output depend on whether `claude` is on the host PATH.
-# Prefer USERPROFILE on Windows.
-mkdir -p "${USERPROFILE:-$HOME}/.cursor"
+# sethome sets HOME on Windows too, so $HOME is enough here.
+mkdir -p "$HOME/.cursor"
 
 title "install two skills"
 trace $CLI experimental aitools install --skills-only --global