fix(weather): read atom-keyed ducts in duct base/strength layers

duct_field/2 did d["base"] || d["base_m"], but ProfilesFile.read/1
atomizes both keys via its @mp_atom_keys whitelist. String indexing an
atom-keyed map returns nil, so the Duct Base and Duct Strength layers
were always nil on the cold-derive path and in point-detail popups —
despite the comment directly above claiming both shapes were handled.

Normalize keys before lookup, the way duct_min_freq/1 already did, and
share that normalization between the two.

lib/microwaveprop/weather/weather_layers.ex

@@ -54,7 +54,7 @@ defmodule Microwaveprop.Weather.WeatherLayers do
   end
 
   defp duct_min_freq(duct) when is_map(duct) do
-    d = Map.new(duct, fn {k, v} -> {to_string(k), v} end)
+    d = stringify_keys(duct)
 
     case d["min_freq_ghz"] do
       f when is_number(f) and f > 0 -> f * 1.0
@@ -198,15 +198,29 @@ defmodule Microwaveprop.Weather.WeatherLayers do
   # wider frequency range, so it's the most meaningful scalar.
   defp duct_field(ducts, "base") do
     ducts
-    |> Enum.map(fn d -> d["base"] || d["base_m"] end)
+    |> Enum.map(&duct_value(&1, ["base", "base_m"]))
     |> Enum.reject(&is_nil/1)
     |> Enum.min(fn -> nil end)
   end
 
   defp duct_field(ducts, "strength") do
     ducts
-    |> Enum.map(fn d -> d["strength"] || d["thickness_m"] end)
+    |> Enum.map(&duct_value(&1, ["strength", "thickness_m"]))
     |> Enum.reject(&is_nil/1)
     |> Enum.max(fn -> nil end)
   end
+
+  # First present key wins. Keys are normalized to strings first because
+  # a duct read back through `ProfilesFile.read/1` carries atom keys
+  # (`:base_m`) while a `Msgpax`-decoded or sounding-derived one carries
+  # strings — indexing an atom-keyed map with a string silently returns
+  # nil, which blanks the layer.
+  defp duct_value(duct, keys) when is_map(duct) do
+    d = stringify_keys(duct)
+    Enum.find_value(keys, fn key -> d[key] end)
+  end
+
+  defp duct_value(_duct, _keys), do: nil
+
+  defp stringify_keys(map), do: Map.new(map, fn {k, v} -> {to_string(k), v} end)
 end

test/microwaveprop/weather/weather_layers_test.exs

@@ -154,6 +154,44 @@ defmodule Microwaveprop.Weather.WeatherLayersTest do
       assert result.duct_base_m == nil
       assert result.duct_strength == nil
     end
+
+    # HrrrNativeClient and the Rust f00 pipeline emit `:base_m` /
+    # `:thickness_m`, which `ProfilesFile.read/1` atomizes via its
+    # `@mp_atom_keys` whitelist. String-key access on an atom-keyed map
+    # returns nil, which blanks the Duct Base / Duct Strength overlays
+    # on every cold-derive read.
+    test "extracts base and strength from atom-keyed native ducts" do
+      ducts = [
+        %{base_m: 500.0, top_m: 800.0, thickness_m: 300.0},
+        %{base_m: 200.0, top_m: 400.0, thickness_m: 200.0}
+      ]
+
+      result = WeatherLayers.derive(sample_row(%{duct_characteristics: ducts}))
+
+      assert result.duct_base_m == 200.0
+      assert result.duct_strength == 300.0
+    end
+
+    test "extracts base and strength from string-keyed native ducts" do
+      ducts = [
+        %{"base_m" => 500.0, "top_m" => 800.0, "thickness_m" => 300.0},
+        %{"base_m" => 200.0, "top_m" => 400.0, "thickness_m" => 200.0}
+      ]
+
+      result = WeatherLayers.derive(sample_row(%{duct_characteristics: ducts}))
+
+      assert result.duct_base_m == 200.0
+      assert result.duct_strength == 300.0
+    end
+
+    test "extracts base and strength from atom-keyed sounding ducts" do
+      ducts = [%{base: 500.0, strength: 12.5}, %{base: 200.0, strength: 8.0}]
+
+      result = WeatherLayers.derive(sample_row(%{duct_characteristics: ducts}))
+
+      assert result.duct_base_m == 200.0
+      assert result.duct_strength == 12.5
+    end
   end
 
   describe "derive/1 duct cutoff frequency" do