test: enable :slow tests by default + add coverage tests across modules
Removed the `exclude: [:slow]` from test_helper.exs — the slow-tagged
wgrib2 fixture tests pass with the binary on PATH and pull
Microwaveprop.Weather.Grib2.Wgrib2 from 23% to 90%+ in coverage runs.
Additional tests:
- Pskr.Client: tcp/tcp_closed/tcp_error stale-socket fall-throughs
- Weather context: weather_point_detail/3, latest_grid_valid_time/0,
available_weather_valid_times/0, available_hrdps_valid_times/0
- PathCompute.compute/4: with HRRR profile near the path
- RoverPathProfileWorker: real Path row + skip-when-complete
- RoverLive: URL stations encoding, add_station error paths
- PathLive: rover_path_id branches (404, malformed UUID)
3599 tests, 0 failures.