- Persist.h: shared writeHeader()/readHeader() for the magic+version+count
on-disk header; Waypoint and Trail snapshots now share one implementation
(byte layout unchanged; each keeps its own count clamp/reject + extra fields).
- TrailScreen: pushAction() guards _act_map / PopupMenu capacity, so adding a
new action can't silently overrun the fixed array.
- PopupMenu: add count()/setSelected() accessors; replace the remaining direct
_sel/_count field pokes in NearbyScreen, TrailScreen and QuickMsgScreen.
- Trail summary: unit-suffixed time ("1h 05m" / "5m 03s") so hours can't be
misread as minutes.
- Trail::haversineMeters delegates to geo::haversineKm — single Haversine
implementation (also trims a little flash).
Verified: GAT562 (SSD1306) and WioTrackerL1Eink (GxEPD) solo builds compile clean.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
