The on-demand loader never retries a tile whose fetch failed, so holes from a
bad signal stayed blank even after the network recovered. Add a healer: every
30s, when OSM is reachable, re-fetch MISSING tiles (current zoom) for the
visible area and along the ridden route, cache them, and redraw. Gentle to OSM
(one-tile probe, 300ms throttle, <=40 fetches/cycle); respects offline mode.
Wired on record/detail/compare/roads maps, stopped on screen change.
4aiman
3f092cced0