docs: hide livebook run-badge, document downloads in the README

ex_doc renders a "Run in Livebook" badge on every .livemd extra with no
way to suppress or platform-gate it, and its livebook.dev/run target
fails to open on the hosted (Linux) Livebooks most visitors reach —
where Emily's macOS / Apple-Silicon NIF can't load anyway.

Hide the badge with a before_closing_head_tag CSS rule (`!important`,
to beat ex_doc's more specific `.content-inner` selector), and add a
note to the README's Livebooks section covering the Apple Silicon
requirement and how to view/download each notebook via its page's
"View Source" link — rather than repeating an admonition in all eight
livebooks.

Author: ausimian

README.md

@@ -320,6 +320,13 @@ End-to-end Livebooks under `livebooks/`. Each one declares its own
 `Mix.install/2` block and pins `Emily.Backend` as the default Nx
 backend, so they're self-contained — open in Livebook and run.
 
+> **Requires Apple Silicon + macOS 14+** (MLX / Metal) — these
+> notebooks won't run on Linux or Intel hosts, including the hosted
+> Livebooks a "Run in Livebook" badge would open. To get a copy, open
+> its page in the Livebooks section of these docs and use the **View
+> Source** link (top-right) to view or download the `.livemd` from
+> GitHub, then run it in Livebook on a Mac.
+
 - **`distilbert_qa.livemd`** — question answering with
   `distilbert-base-uncased-distilled-squad`.
 - **`qwen3_quantized.livemd`** — Qwen3-0.6B int4-quantized via the

mix.exs

@@ -208,6 +208,7 @@ defmodule Emily.MixProject do
     [
       main: "readme",
       source_url_pattern: "#{@source_url}/blob/#{@version}/%{path}#L%{line}",
+      before_closing_head_tag: &before_closing_head_tag/1,
       # Symbols ExDoc can't link, so it warns on every reference to them.
       # Listed explicitly on purpose: the `mix precommit` docs gate fails
       # with the exact unlinkable symbol when a new one appears, making each
@@ -266,6 +267,18 @@ defmodule Emily.MixProject do
     ]
   end
 
+  # ex_doc renders a "Run in Livebook" badge on every `.livemd` extra
+  # (extra_template.eex) with no option to suppress it. Emily's NIF is
+  # macOS / Apple-Silicon only, and the badge's `livebook.dev/run` target
+  # fails to open on the hosted (Linux) Livebooks most visitors reach, so
+  # we hide it — each livebook links to its GitHub source/download instead.
+  # `!important` is required to beat ex_doc's more specific
+  # `.content-inner .livebook-badge-container { display: flex }` rule.
+  defp before_closing_head_tag(:html),
+    do: ~s(<style>.livebook-badge-container{display:none!important}</style>)
+
+  defp before_closing_head_tag(_), do: ""
+
   defp package do
     [
       licenses: ["MIT"],