fix: made the macos app smaller

mix.exs

@@ -62,11 +62,21 @@ defmodule BDS.MixProject do
       {:ex_ratatui, "~> 0.11"},
       {:image, "~> 0.67"},
       {:nx, "~> 0.10"},
-      {:exla, "~> 0.10"},
+      # Only one ML inference backend ships per platform; NIF releases are
+      # host-built, so the build OS is the target OS. EXLA (283 MB XLA CPU
+      # payload) never runs in the macOS app — EMLX always wins on Apple
+      # Silicon — but `runtime: false` alone can't exclude it there because
+      # the `image` dep declares exla as an optional application, which drags
+      # it into the release whenever it exists in the prod dep tree. Scoping
+      # it to dev/test on macOS keeps it fully out of macOS releases while
+      # Linux/Windows ship it as their production inference backend.
+      {:exla, "~> 0.10", if(macos?(), do: [only: [:dev, :test]], else: [])},
       # Apple Silicon GPU (Metal) acceleration for embedding inference. Ships
       # precompiled MLX binaries; the Neural backend prefers it on arm64 macOS
-      # and falls back to EXLA-CPU elsewhere (SPECGAPS A1-14c).
-      {:emlx, "~> 0.2.0"},
+      # and falls back to EXLA-CPU elsewhere (SPECGAPS A1-14c). Apple-only, so
+      # non-macOS releases exclude it (runtime: false deps stay out of
+      # releases — nothing pulls emlx in optionally, unlike exla above).
+      {:emlx, "~> 0.2.0", runtime: macos?()},
       {:bumblebee, "~> 0.6.3"},
       {:hnswlib, "~> 0.1.7"},
       {:stemex, "~> 0.2.1"},
@@ -121,4 +131,6 @@ defmodule BDS.MixProject do
       ]
     ]
   end
+
+  defp macos?, do: :os.type() == {:unix, :darwin}
 end