Relocate the miner-update control from a standalone full-width button into the mining-control
header row, immediately left of the benchmark button:
- The button now shows the latest available version ("Update <tag>"), with the current installed
version as text to its left ("Current: <tag>" / "none").
- A one-shot background version check (util::XmrigUpdater::startCheck) runs the first time the pool
section is shown, so the latest tag can be displayed; until it arrives the button reads
"Update miner…". Clicking opens the existing dialog; disabled (greyed, with tooltip) while the
miner is running.
- New i18n keys: xmrig_update_short, xmrig_current, xmrig_none.
Both variants build; suite passes; GUI smoke-launched without crash.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>