feat(cli): restore automatic update policy - #47161

Summary

• restore update: "auto" and migrate legacy autoupdate: true to it
• run one CLI-owned update check on every TUI startup for both notify and auto policies
• poll from every locally running server after one minute and every ten minutes thereafter
• install automatic updates without restarting the running server
• publish server-side available and installed outcomes through the existing installation events
• show notify-mode and installed-update messages beneath the Home prompt, opening the install dialog only for available updates
• regenerate Protocol, client, and website surfaces

Testing

• 30 focused CLI updater, polling, and installation tests
• 4 focused Core config migration/loading tests
• focused TUI Home notification, server-event, and lifecycle tests
• Server process event-stream test
• Protocol and Website generated-file checks
• git diff --check
• local typecheck not run per request