ci: add shellcheck workflow, install/uninstall scripts

uninstall.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# Remove global git hooks configuration set by install.sh.
+
+set -euo pipefail
+
+if git config --global --get core.hooksPath > /dev/null 2>&1; then
+	git config --global --unset core.hooksPath
+	echo "Removed core.hooksPath"
+elif git config --global --get init.templateDir > /dev/null 2>&1; then
+	git config --global --unset init.templateDir
+	echo "Removed init.templateDir"
+else
+	echo "No global hooks configuration found."
+	exit 0
+fi
+
+echo "Global hooks configuration cleared."