Each fix is covered by a regression test that fails on `main` and
passes on this commit.
Round 1 (initial review):
* propagation: thread `latitude` into the conditions map so
`score_season/4` actually picks up regional multipliers
* hrrr_client / fetcher.rs: `nearest_hrrr_hour` rounds DOWN, never at
a future cycle that NOAA hasn't published yet
* radio: spherical-vector great-circle midpoint replaces the
arithmetic mean — anti-meridian paths no longer fold to Greenwich
* weather: `reconcile_weather_statuses` scales the longitude band by
`1 / cos(lat)` so the bbox stays ~150 km wide at every latitude
* radio/maidenhead: clamp 90°/180° below the field-bucket overflow so
`from_latlon` never emits invalid characters like 'S'
* prop_grid_rs/pipeline: merge HRRR + NEXRAD-derived rain rates and
read `best_duct_freq_ghz` into `best_duct_band_ghz` so the Native
Duct Boost actually fires
* propagation/region (Elixir + Rust): inclusive upper bounds so points
exactly at lat_max get the regional multiplier
* weather/sounding_params (Elixir + Rust): drop the 10 m gradient
floor so HRRR's thin near-surface layers stop hiding sharp ducts
* weather/sounding_params: when the profile ends inside a duct,
finalize it with the highest sample as the top instead of throwing
it away (Rust port already correct)
Round 2 (post-fix sweep):
* radio + commercial: single canonical haversine in Radio (atan2
form); Commercial delegates instead of carrying a second copy that
could disagree at threshold distances
* prop_grid_rs/profiles_file: `snap_coords` matches Elixir's
step-aware snap (`round(coord/0.125) * 0.125`, then 3-dp round) so
Rust-keyed and Elixir-keyed profile maps land on the same cell
* weather/grib2/wgrib2: `parse_lon_val_segment` uses `Float.parse`
uniformly — wgrib2 dropping the trailing `.0` from a longitude no
longer crashes the whole chain step
Graham McIntire
6aa91e7656