Add record chat sheet with OpenAI streaming

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/music_library/record_chat.ex

@@ -0,0 +1,50 @@
+defmodule MusicLibrary.RecordChat do
+  alias MusicLibrary.Records.{Record, Similarity}
+
+  def stream_response(messages, record, embedding_text, callback) do
+    system_prompt = build_system_prompt(record, embedding_text)
+
+    full_messages = [
+      %{role: "system", content: system_prompt} | messages
+    ]
+
+    OpenAI.chat_stream(full_messages, on_chunk: callback)
+  end
+
+  def get_embedding_text(record_id) do
+    Similarity.get_embedding_text(record_id)
+  end
+
+  def build_system_prompt(%Record{} = record, embedding_text) do
+    context =
+      case embedding_text do
+        nil -> basic_context(record)
+        "" -> basic_context(record)
+        text -> text
+      end
+
+    """
+    You are a knowledgeable music assistant. Answer questions about the album \
+    the user is currently viewing. Use the provided information as your primary \
+    reference. Be concise and accurate. When unsure, say so.
+
+    Album information:
+    #{context}
+    """
+  end
+
+  defp basic_context(%Record{} = record) do
+    artist_names = Record.artist_names(record)
+    genres = Enum.join(record.genres || [], ", ")
+
+    """
+    Album: #{record.title}
+    Artists: #{artist_names}
+    Genres: #{genres}
+    Released: #{record.release_date || "Unknown"}
+    Type: #{record.type}
+    Format: #{record.format}
+    """
+    |> String.trim()
+  end
+end