migration guide additions & fix refs build (#1190)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: mdrxy

reference/python/mkdocs.yml

@@ -228,6 +228,7 @@ plugins:
               # Preload modules before collecting documentation to enable cross-references
               - langchain
               - langchain_core
+              - langgraph
               - langsmith
 
             # Generate objects.inv file for this site to enable cross-referencing from other sites

src/oss/python/migrate/langchain-v1.mdx

@@ -936,9 +936,9 @@ Existing functionality outside the focus of standard interfaces and agents has b
 
 Methods, functions, and other objects that were already deprecated and slated for removal in 1.0 have been deleted. Check the [deprecation notices](https://python.langchain.com/docs/versions/migrating_chains) from previous versions for replacement APIs.
 
-### `.text()` is now a property
+### Text property
 
-Use of the `.text()` method on message objects should drop the parentheses:
+Use of the `.text()` method on message objects should drop the parentheses, as it is now a property:
 
 ```python
 # Property access
@@ -948,4 +948,16 @@ text = response.text
 text = response.text()
 ```
 
-Existing usage patterns (i.e., `.text()`) will continue to function but now emit a warning.
+Existing usage patterns (i.e., `.text()`) will continue to function but now emit a warning. The method form will be removed in v2.
+
+### `example` parameter removed from `AIMessage`
+
+The `example` parameter has been removed from @[`AIMessage`] objects. We recommend migrating to use `additional_kwargs` for passing extra metadata as needed.
+
+## Minor changes
+
+- `AIMessageChunk` objects now include a `chunk_position` attribute with position `'last'` to indicate the final chunk in a stream. This allows for clearer handling of streamed messages. If the chunk is not the final one, `chunk_position` will be `None`.
+- `LanguageModelOutputVar` is now typed to @[`AIMessage`] instead of @[`BaseMessage`].
+- The logic for merging message chunks (`AIMessageChunk.add`) has been updated with more sophisticated selection handling for the final id for the merged chunk. It prioritizes provider-assigned IDs over LangChain-generated IDs.
+- We now open files with `utf-8` encoding by default.
+- Standard tests now use multimodal content blocks.