/weather mount called Weather.latest_weather_grid/1 directly, which
runs WeatherLayers.derive over 92k cells and Jason-encodes the
result. Production HTTP logs showed dead renders consistently
landing at 9.8–10.2 s — right at LiveView's socket join deadline.
The browser would render half the page, the WS would fail to mount,
and the user saw "attempting to reconnect".
The JS hook already fires map_bounds via requestAnimationFrame
immediately after mount, and the existing handle_event("map_bounds")
path returns viewport-scoped weather data via the update_weather
push event. So the dead-render data fetch is redundant — drop it.
Mount now returns initial_data_json: "[]"; the layer paints
~50–200 ms after WS connect via the bounds-driven flow.
Graham McIntire
2e5b61f2f9