fix: make installer gate portable in root CI

package.json

@@ -1,6 +1,6 @@
 {
   "name": "tallynote",
-  "version": "1.1.15",
+  "version": "1.1.16",
   "private": true,
   "type": "module",
   "packageManager": "pnpm@9.0.6",

scripts/test-installer.sh

@@ -88,6 +88,12 @@ bash -c '
   chmod 700 "$mode_dir"
   [[ "$(stat_mode_bits "$mode_dir")" == 448 ]]
   mkdir -p "$owner_parent"
+  # CI runs this shell suite as root. Make the parent genuinely non-root in
+  # that environment so the assertion exercises the ownership guard instead
+  # of accidentally passing because root-owned parents are allowed.
+  if [[ "${EUID:-$(id -u)}" == 0 ]]; then
+    chown 65534:65534 "$owner_parent"
+  fi
   if (assert_path_chain "$owner_parent/child") >/dev/null 2>&1; then
     echo "expected non-root path parent to fail" >&2
     exit 1