Squid 1.8.9 — Windows + Linux Tentacle lifecycle PR gates - PR-gated Windows tentacle lifecycle smoke E2E (service + blue-green upgrade); required status check via the 3-job sentinel pattern (#407, #408) - Fix install-script E2E flakiness: UAC exit-code propagation + per-test ProgramData isolation; non-breaking install-tentacle.ps1 elevation-seam refactor; re-gate install-script category (#409) - PR-gated Linux blue-green versioned-upgrade smoke E2E; required status check, symmetric with Windows (#410)