Adds tools/trail_export.py: auto-detects the Wio port, waits for the
<?xml header, captures bytes until </gpx>, and writes a timestamped file
to tools/gpx/. Replaces the abandoned synthetic-FAT USB-MSC approach with
a simple host-side script.
- README: new "GPX Trail Export" section
- tools_screen.md: trail_export.py shown as the recommended download path,
cat/PuTTY kept as a manual fallback
- .gitignore: ignore tools/gpx/ output dir (mirrors tools/pngs/)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
