feat(contents_shinychat): Add new contents_shinychat() and contents_shinychat_chunk()

These new functions are the singledispatch equivalent of the previous normalize_message() and normalize_message_chunk(). Although not quite as flexible as the previous strategies pattern, it's much simpler (implementation wise and also for those registering new methods) and aligns much better with the vision for the R package

Author: cpsievert

pkg-py/src/shinychat/__init__.py

@@ -1,4 +1,12 @@
 from ._chat import Chat, chat_ui
+from ._chat_normalize import contents_shinychat, contents_shinychat_chunk
 from ._markdown_stream import MarkdownStream, output_markdown_stream
 
-__all__ = ["Chat", "chat_ui", "MarkdownStream", "output_markdown_stream"]
+__all__ = [
+    "Chat",
+    "chat_ui",
+    "MarkdownStream",
+    "output_markdown_stream",
+    "contents_shinychat",
+    "contents_shinychat_chunk",
+]

pkg-py/src/shinychat/_chat.py

@@ -52,7 +52,7 @@
     is_chatlas_chat_client,
     set_chatlas_state,
 )
-from ._chat_normalize import normalize_message, normalize_message_chunk
+from ._chat_normalize import contents_shinychat, contents_shinychat_chunk
 from ._chat_provider_types import (
     AnthropicMessage,
     GoogleMessage,
@@ -636,7 +636,7 @@ async def append_message(
             self._pending_messages.append((message, False, "append", None))
             return
 
-        msg = normalize_message(message)
+        msg = contents_shinychat(message)
         msg = await self._transform_message(msg)
         if msg is None:
             return
@@ -753,7 +753,7 @@ async def _append_message_chunk(
         self._current_stream_id = stream_id
 
         # Normalize various message types into a ChatMessage()
-        msg = normalize_message_chunk(message)
+        msg = contents_shinychat_chunk(message)
 
         if operation == "replace":
             self._current_stream_message = (