ci: add shellcheck workflow, install/uninstall scripts

install.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+# Install git hooks globally via core.hooksPath.
+# Usage: ./install.sh [--template]
+#   --template  Use init.templateDir instead (only affects new repos)
+
+set -euo pipefail
+
+hook_dir="$(cd "$(dirname "$0")" && pwd)"
+
+if [ "${1:-}" = "--template" ]; then
+	git config --global init.templateDir "$hook_dir"
+	echo "Installed: init.templateDir set to $hook_dir"
+	echo "New repos created with git init/clone will copy these hooks."
+else
+	git config --global core.hooksPath "$hook_dir"
+	echo "Installed: core.hooksPath set to $hook_dir"
+	echo "All repos will use hooks from $hook_dir."
+fi