Single-slot persistence as agreed. Action popup grows three entries
(conditional on what makes sense for the current state):
- "Save trail" — writes the current RAM ring to /trail in LittleFS.
- "Load trail" — only shown when /trail exists; replaces the live ring
with the snapshot (any active session ends first).
- "Export GPX" — dumps the trail as a minimal GPX 1.1 document over
Serial so the user can capture it from a USB host.
Plumbing:
- TrailStore gains writeTo / readFrom (template on the file handle, so
the platform-specific File flavour stays out of Trail.h) plus
exportGpx(Stream&) for the GPX serializer. Header carries magic
"TRAL", a version byte, point count, and the accumulated active time
so elapsed survives the round trip.
- DataStore::openWrite is exposed publicly so callers outside DataStore
don't have to duplicate the platform open-mode dance.
- MyMesh gains a public getDataStore() accessor.
After Load, _pending_seg_break is set so any subsequent Start opens a
new segment instead of joining the loaded last point.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Save last known unix timestamp to /rtc_save on shutdown and restore it
on startup, so the clock shows correct time immediately after restart
without waiting for GPS fix.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
