Fix all 12 dialyzer warnings

- Replace MapSet with plain list + `in` (features.ex, scorer_diff.ex)
- Remove undefined Beacon.t() type reference (range_estimate.ex)
- Remove dead else branch in find_region (inversion.ex)
- Handle Nx special values in to_float catch-all (recalibrator.ex)
- Remove unreachable catch-all clauses (hrrr_native_client.ex, ncei_metar_client.ex)
- Remove unnecessary nil guards on always-typed values (show.ex)
- Remove dead sky_note/wind_note non-nil clauses (show.ex)
- Remove dead if-guard on always-truthy derive result (hrrr_native_derive.ex)
- Add @spec to path_integrated_conditions (scorer.ex)

lib/microwaveprop/backtest/features.ex

@@ -33,24 +33,23 @@ defmodule Microwaveprop.Backtest.Features do
   and placeholder stubs that always return nil.
   """
   def all_features do
-    excluded =
-      MapSet.new([
-        # 4-arity helper
-        :duct_usable_for_band,
-        # Stubs (always nil)
-        :distance_to_front,
-        :parallel_to_front,
-        # Dead features — no discrimination in consolidated backtest (2026-04-11)
-        :duct_usable_10ghz,
-        :duct_usable_24ghz,
-        :duct_usable_47ghz,
-        :bulk_richardson
-      ])
+    excluded = [
+      # 4-arity helper
+      :duct_usable_for_band,
+      # Stubs (always nil)
+      :distance_to_front,
+      :parallel_to_front,
+      # Dead features — no discrimination in consolidated backtest (2026-04-11)
+      :duct_usable_10ghz,
+      :duct_usable_24ghz,
+      :duct_usable_47ghz,
+      :bulk_richardson
+    ]
 
     :functions
     |> __MODULE__.__info__()
     |> Enum.filter(fn {_name, arity} -> arity == 3 end)
-    |> Enum.reject(fn {name, _} -> MapSet.member?(excluded, name) end)
+    |> Enum.reject(fn {name, _} -> name in excluded end)
     |> Map.new(fn {name, _} ->
       {to_string(name), &apply(__MODULE__, name, [&1, &2, &3])}
     end)

lib/microwaveprop/beacons/range_estimate.ex

@@ -59,7 +59,7 @@ defmodule Microwaveprop.Beacons.RangeEstimate do
   points within range where the estimated received signal exceeds the
   detection floor.
   """
-  @spec estimate(Microwaveprop.Beacons.Beacon.t()) :: map()
+  @spec estimate(struct()) :: map()
   def estimate(beacon) do
     band_mhz = nearest_band_mhz(beacon.frequency_mhz)
     band_config = BandConfig.get(band_mhz)

lib/microwaveprop/propagation/inversion.ex

@@ -65,21 +65,13 @@ defmodule Microwaveprop.Propagation.Inversion do
 
   defp find_region([], _base), do: nil
 
-  defp find_region([pair | rest], base) do
+  defp find_region([pair | rest], _base) do
     [{{_h1, t1}, _i1}, {{_h2, t2}, i2}] = pair
 
-    if is_nil(base) do
-      if t2 > t1 do
-        find_region_top(rest, i2 - 1, i2)
-      else
-        find_region(rest, nil)
-      end
+    if t2 > t1 do
+      find_region_top(rest, i2 - 1, i2)
     else
-      if t2 < t1 do
-        {base, i2 - 1}
-      else
-        find_region(rest, base)
-      end
+      find_region(rest, nil)
     end
   end
 

lib/microwaveprop/propagation/recalibrator.ex

@@ -311,5 +311,5 @@ defmodule Microwaveprop.Propagation.Recalibrator do
 
   defp to_float(n) when is_float(n), do: n
   defp to_float(n) when is_integer(n), do: n * 1.0
-  defp to_float(n), do: n * 1.0
+  defp to_float(_), do: 0.0
 end

lib/microwaveprop/propagation/scorer.ex

@@ -385,6 +385,7 @@ defmodule Microwaveprop.Propagation.Scorer do
   - Other factors (temp, dewpoint, PWAT, BL depth): use path AVERAGE
   - Time/season/sky: taken from first profile (same for entire path)
   """
+  @spec path_integrated_conditions([map()], map()) :: map() | nil
   def path_integrated_conditions(profiles, contact) do
     lon = Kernel.||(contact.pos1["lon"] || contact.pos1["lng"], -97.0)
 

lib/microwaveprop/weather/hrrr_native_client.ex

@@ -242,8 +242,6 @@ defmodule Microwaveprop.Weather.HrrrNativeClient do
     |> Enum.min(fn -> 0.0 end)
   end
 
-  defp min_m_gradient(_), do: nil
-
   defp max_duct_thickness([]), do: nil
   defp max_duct_thickness(ducts), do: ducts |> Enum.map(& &1.thickness_m) |> Enum.max()
 

lib/microwaveprop/weather/ncei_metar_client.ex

@@ -161,7 +161,6 @@ defmodule Microwaveprop.Weather.NceiMetarClient do
   defp parse_metar_temp(s), do: String.to_integer(s) * 1.0
 
   defp c_to_f(c) when is_number(c), do: c * 9.0 / 5.0 + 32.0
-  defp c_to_f(_), do: nil
 
   defp extract_wind_speed(parts) do
     with wind when is_binary(wind) <- Enum.find(parts, &Regex.match?(~r/^\d{3}\d{2,3}KT/, &1)),

lib/microwaveprop_web/live/contact_live/show.ex

@@ -577,9 +577,13 @@ defmodule MicrowavepropWeb.ContactLive.Show do
 
       <%= if @editing do %>
         <div class="bg-base-200 rounded-box p-4 mb-4">
-          <h3 class="font-semibold mb-3">{if admin?(assigns), do: "Edit Contact", else: "Suggest Edit"}</h3>
+          <h3 class="font-semibold mb-3">
+            {if admin?(assigns), do: "Edit Contact", else: "Suggest Edit"}
+          </h3>
           <p class="text-sm opacity-70 mb-4">
-            {if admin?(assigns), do: "Change any fields below. Changes will be applied immediately.", else: "Change any fields below. Only fields you modify will be submitted for review."}
+            {if admin?(assigns),
+              do: "Change any fields below. Changes will be applied immediately.",
+              else: "Change any fields below. Only fields you modify will be submitted for review."}
           </p>
           <.form
             for={@edit_form}
@@ -1503,7 +1507,7 @@ defmodule MicrowavepropWeb.ContactLive.Show do
       samples: length(ep.points),
       dist: format_dist(ep.dist_km),
       source: "SRTM 1-arcsecond",
-      duct_count: length(ep.ducts || [])
+      duct_count: length(ep.ducts)
     }
   end
 
@@ -1768,7 +1772,7 @@ defmodule MicrowavepropWeb.ContactLive.Show do
   end
 
   defp time_note(ts, lon) do
-    solar_hour = ts.hour + ts.minute / 60 + (lon || 0) / 15
+    solar_hour = ts.hour + ts.minute / 60 + lon / 15
     solar_hour = rem_float(solar_hour + 24, 24)
     h = round(solar_hour)
 
@@ -1817,7 +1821,6 @@ defmodule MicrowavepropWeb.ContactLive.Show do
   end
 
   defp sky_note(nil), do: "—"
-  defp sky_note(pct), do: "#{round(pct)}% cloud cover"
 
   defp season_note(month, band_config) do
     month_names = ~w(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec)
@@ -1828,20 +1831,6 @@ defmodule MicrowavepropWeb.ContactLive.Show do
 
   defp wind_note(nil), do: "—"
 
-  defp wind_note(kts) do
-    k = Float.round(kts, 1)
-
-    label =
-      cond do
-        k < 5 -> "calm"
-        k < 15 -> "light"
-        k < 25 -> "moderate"
-        true -> "strong"
-      end
-
-    "#{k} kts (#{label})"
-  end
-
   defp rain_note(rate) when rate > 0, do: "#{Float.round(rate, 1)} mm/hr"
   defp rain_note(_), do: "None"
 

lib/mix/tasks/hrrr_native_derive.ex

@@ -40,16 +40,12 @@ defmodule Mix.Tasks.HrrrNativeDeriveFields do
       Enum.count(profiles, fn profile ->
         derived = derive(profile)
 
-        if derived do
-          {1, _} =
-            HrrrNativeProfile
-            |> where([p], p.id == ^profile.id)
-            |> Repo.update_all(set: derived)
+        {1, _} =
+          HrrrNativeProfile
+          |> where([p], p.id == ^profile.id)
+          |> Repo.update_all(set: derived)
 
-          true
-        else
-          false
-        end
+        true
       end)
 
     Mix.shell().info("Updated #{count} profiles with derived turbulence fields.")

lib/mix/tasks/scorer_diff.ex

@@ -63,18 +63,16 @@ defmodule Mix.Tasks.ScorerDiff do
   end
 
   defp validate_weight_keys!(weights) do
-    expected_keys =
-      MapSet.new(~w(humidity time_of_day td_depression refractivity sky season wind rain pressure pwat))
+    expected_keys = ~w(humidity time_of_day td_depression refractivity sky season wind rain pressure pwat)
+    provided_keys = Map.keys(weights)
 
-    provided_keys = MapSet.new(Map.keys(weights))
-
-    missing = MapSet.difference(expected_keys, provided_keys)
-    extra = MapSet.difference(provided_keys, expected_keys)
+    missing = expected_keys -- provided_keys
+    extra = provided_keys -- expected_keys
 
     errors =
       []
-      |> prepend_if(MapSet.size(missing) > 0, "Missing: #{inspect(MapSet.to_list(missing))}")
-      |> prepend_if(MapSet.size(extra) > 0, "Extra: #{inspect(MapSet.to_list(extra))}")
+      |> prepend_if(missing != [], "Missing: #{inspect(missing)}")
+      |> prepend_if(extra != [], "Extra: #{inspect(extra)}")
 
     if errors != [] do
       Mix.raise("Invalid weight keys. " <> Enum.join(errors, " "))