* Reapply "Always revalidate desktop updates before install"
This reverts commit 623c05aa4d.
* fix(desktop): make update revalidation safe on quit
Updater-triggered quits now bypass normal quit handling, and manifest revalidation gives up after five seconds without allowing a late install.
* fix(desktop): preserve fail-closed update installs
Keep cached updates deferred when quit-time validation is offline, and report validation timeouts separately from superseded releases.
* fix(desktop): preserve updater quit behavior
Automatic installs remain silent without relaunching, updater handoff is bounded, and background preparation failures remain visible without pinning manifest checks.
* fix(desktop): keep AppImage updates manual
Preserve the AppImage safety exemption by skipping ordinary quit-time installation while retaining the explicit Update now path.
* fix(desktop): serialize update preparation
* fix(desktop): recognize macOS updater quit handoff
* fix(desktop): report found app updates during manual checks
Manual checks could reuse cached update state while the renderer discarded pending update details. Keep found update versions visible while downloads prepare, and reserve install affordances for ready updates.
* test(desktop): cover manual update retry after errors
* fix(desktop): keep ready updates ready on recheck
* fix(desktop): show app update check feedback
Manual desktop app update checks now leave visible status feedback even when the shared update state is pending or available. Updater check and preparation errors are carried through the existing result path so the settings row and callout can show the failure instead of only logging it.
* fix(desktop): make update retries perform fresh checks
Manual retries now clear runtime errors emitted by a failed check so the next click calls the updater again. Background checks also skip while a visible manual check is active, and last-checked update copy uses complete localized strings.
* fix(desktop): punctuate update check timestamp copy
* fix(desktop): share runtime update errors
* fix(desktop): preserve update preparation errors
* fix(desktop): settle update check review races
* fix(desktop): settle quiet update check errors
* fix(desktop): handle overlapping update checks
* fix(desktop): preserve preparation errors during checks
Automatic desktop update checks still respect rollout admission. Manual checks carry an explicit intent through the app and desktop updater service, and the up-to-date state now shows when the last check completed.
