CLI: make `daemon_auto_start` opt-in — a persistent, self-updating background daemon shouldn't be the default

Since Codex CLI 0.157.0, opening an interactive codex session on Linux (WSL2) can:

1. Start a persistent background daemon (codex app-server --managed-daemon) that survives after all Codex windows close until codex app-server daemon stop or reboot.
2. Copy the whole platform package (~374 MB) into ~/.codex/packages/app-server-daemon/releases/ and run the daemon from that copy, decoupling backend version from the npm-installed CLI.
3. Start a detached updater (codex app-server daemon pid-update-loop) that checks for updates after 5 minutes and hourly, downloading new releases and restarting the backend.
4. Pin environment from the first session that started the daemon (e.g. HTTPS_PROXY), affecting later sessions.

The reporter requests daemon_auto_start be opt-in (default false) for CLI users, or at minimum prompt once. Workaround:

codex features disable daemon_auto_start
codex app-server daemon stop
pkill -f 'app-server daemon pid-update-loop'
rm -rf ~/.codex/packages/app-server-daemon

Bug: codex app-server daemon stop stops the app-server but may leave the pid-update-loop running.

Discussion on 2026-10-12 escalated on Hacker News, with commenters comparing behavior to malware and citing lack of clear documentation for daemon_auto_start in official config references. OpenAI release notes described only “automatic background-server startup for eligible interactive sessions.”

Related issues: #40969 (updater kills in-flight turns), #41188, #46468, #48050 (package manager installs), #42457, #37537 (environment inheritance).