Move ML deps to dev/test only, exclude from production build

- Nx, Axon, EXLA, Polaris deps restricted to only: [:dev, :test]
- model.ex and training mix tasks moved to lib_ml/ (compiled via
  elixirc_paths in dev/test only)
- load_ml_model uses Code.ensure_loaded? + apply/3 to avoid
  compile-time references to ML modules in production
- Verified: MIX_ENV=prod compiles clean with no ML warnings

config/dev.exs

@@ -86,6 +86,9 @@ config :microwaveprop, Oban,
 # Enable dev routes for dashboard and mailbox
 config :microwaveprop, dev_routes: true
 
+# Load ML model at startup (Nx/Axon/EXLA only available in dev/test)
+config :microwaveprop, load_ml_model: true
+
 # Use local SRTM1 tiles for elevation lookups instead of the Open-Meteo API
 config :microwaveprop, srtm_tiles_dir: Path.expand("~/srtm/tiles")
 

lib/microwaveprop/application.ex

@@ -25,8 +25,10 @@ defmodule Microwaveprop.Application do
     opts = [strategy: :one_for_one, name: Microwaveprop.Supervisor]
     result = Supervisor.start_link(children, opts)
 
-    # Load ML model after supervision tree is up (non-blocking, no-op if file missing)
-    Microwaveprop.Propagation.load_ml_model()
+    # Load ML model in dev/test only (Nx/Axon not compiled for prod)
+    if Application.get_env(:microwaveprop, :load_ml_model, false) do
+      Microwaveprop.Propagation.load_ml_model()
+    end
 
     result
   end

lib/microwaveprop/propagation.ex

@@ -6,7 +6,6 @@ defmodule Microwaveprop.Propagation do
   alias Microwaveprop.Propagation.BandConfig
   alias Microwaveprop.Propagation.Grid
   alias Microwaveprop.Propagation.GridScore
-  alias Microwaveprop.Propagation.Model
   alias Microwaveprop.Propagation.Scorer
   alias Microwaveprop.Repo
   alias Microwaveprop.Weather.SoundingParams
@@ -14,22 +13,28 @@ defmodule Microwaveprop.Propagation do
   require Logger
 
   @ml_key :propagation_ml
+  @ml_module Microwaveprop.Propagation.Model
 
   @doc """
   Loads the ML model from disk, compiles the predict function, and caches both
-  in persistent_term. No-op if the model file doesn't exist.
+  in persistent_term. No-op if the model file doesn't exist or ML deps unavailable.
   """
   def load_ml_model do
-    case Model.load() do
-      {:ok, params} ->
-        predict_fn = Model.compile_predict()
-        :persistent_term.put(@ml_key, {predict_fn, params})
-        Logger.info("PropagationML: model loaded and compiled from #{inspect(Model.default_path())}")
-        :ok
+    if Code.ensure_loaded?(@ml_module) do
+      case apply(@ml_module, :load, []) do
+        {:ok, params} ->
+          predict_fn = apply(@ml_module, :compile_predict, [])
+          :persistent_term.put(@ml_key, {predict_fn, params})
+          Logger.info("PropagationML: model loaded and compiled")
+          :ok
 
-      :error ->
-        Logger.info("PropagationML: no model file found, using algorithm scorer only")
-        :ok
+        :error ->
+          Logger.info("PropagationML: no model file found, using algorithm scorer only")
+          :ok
+      end
+    else
+      Logger.info("PropagationML: ML dependencies not available")
+      :ok
     end
   end
 

mix.exs

@@ -32,7 +32,8 @@ defmodule Microwaveprop.MixProject do
   end
 
   # Specifies which paths to compile per environment.
-  defp elixirc_paths(:test), do: ["lib", "test/support"]
+  defp elixirc_paths(:test), do: ["lib", "lib_ml", "test/support"]
+  defp elixirc_paths(:dev), do: ["lib", "lib_ml"]
   defp elixirc_paths(_), do: ["lib"]
 
   # Specifies your project dependencies.
@@ -65,10 +66,10 @@ defmodule Microwaveprop.MixProject do
       {:oban, "~> 2.19"},
       {:credo, "~> 1.7", only: [:dev, :test], runtime: false},
       {:earmark, "~> 1.4"},
-      {:nx, "~> 0.9"},
-      {:axon, "~> 0.7"},
-      {:exla, "~> 0.9"},
-      {:polaris, "~> 0.1"}
+      {:nx, "~> 0.9", only: [:dev, :test]},
+      {:axon, "~> 0.7", only: [:dev, :test]},
+      {:exla, "~> 0.9", only: [:dev, :test]},
+      {:polaris, "~> 0.1", only: [:dev, :test]}
     ]
   end