chore(shellcheck): no new findings in the update skill, lib.sh and install.sh (Issue #72)

CI now shellchecks the update skill's scripts: SC1091 is disabled at their
`source` lines as in the other skills, and the two findings this branch added
(lib.sh's loop_lock.sh source, install.sh's one-item legacy loop) are
disabled at their lines.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

deploy/install.sh

@@ -167,6 +167,7 @@ if [ "$REFRESH" -eq 1 ] || [ "${MAM_SKIP_VENV:-0}" -eq 1 ] || ! check_assets_pre
 
   # Migrate legacy root layout for remove.sh into .mam_deploy/ if owned
   mkdir -p .mam_deploy
+  # shellcheck disable=SC2043  # one legacy script left (update.sh went with Issue #72)
   for legacy_script in remove.sh; do
     if [ -f "$legacy_script" ] && grep -Fqx "$legacy_script" "$MANIFEST_FILE" 2>/dev/null; then
       mv -f "$legacy_script" ".mam_deploy/$legacy_script"