* [client] Clear stale installer result before starting update
The installer result file could survive a previous update attempt (e.g.
when the updater wrote it after the restarted daemon already ran its
startup check). A new install attempt left the old file in place, so the
GUI progress window's first GetInstallerResult poll read the outdated
result: a stale success made the GUI quit mid-install, which cancelled
the TriggerUpdate context and aborted the artifact verification; a stale
error surfaced a bogus failure dialog for a succeeding update.
Remove any leftover result file at the start of RunInstallation, before
the download begins, so result watchers only see the current attempt's
outcome.
* [client] Align stale-result warning with log message style
Auto-update logic moved out of the UI into a dedicated updatemanager.Manager service that runs in the connection layer. The
UI no longer polls or checks for updates independently.
The update manager supports three modes driven by the management server's auto-update policy:
No policy set by mgm: checks GitHub for the latest version and notifies the user (previous behavior, now centralized)
mgm enforces update: the "About" menu triggers installation directly instead of just downloading the file — user still initiates the action
mgm forces update: installation proceeds automatically without user interaction
updateManager lifecycle is now owned by daemon, giving the daemon server direct control via a new TriggerUpdate RPC
Introduces EngineServices struct to group external service dependencies passed to NewEngine, reducing its argument count from 11 to 4
Viktor Liu