New LiveView at /weather-ca duplicates the /weather UI but defaults the
viewport to central Canada (55N, -100W, z=4) and renders the map div
with data-source="hrdps". The JS hook reads that attribute and appends
&source=hrdps to every cell fetch; the WeatherTileController routes
those reads through Weather.weather_grid_hrdps_at/2, which only reads
the <vt>.hrdps scalar dir and skips HRRR merging entirely. Timeline is
sourced from ScalarFile.list_valid_times_hrdps/0 so HRDPS-only hours
show up even when no HRRR file exists for the same valid_time.
Also drops "— Unified" from the algo.md H1.
