A launch from the Dock, the Start menu or a launcher has no terminal, and
without RUST_LOG nothing reached standard error anyway, so start-up and
GPU warnings were lost unless Help > Enable Logging was already on.
The logger now writes EffectCraft's info records and everyone's warnings
to standard error and to Logs/effectcraft.log in the settings folder.
Each launch keeps the previous two runs' logs; the file is capped at
16 MiB. RUST_LOG still overrides the filter. Help > Reveal Logging File
shows this run's log unless Enable Logging is on.
Ported from storytold/pdfcraft#239.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
