ollama: thinking, tool streaming, docs, tests (#31772)

* New `reasoning` (bool) param to support toggling [Ollama
thinking](https://ollama.com/blog/thinking) (#31573, #31700). If
`reasoning=True`, Ollama's `thinking` content will be placed in the
model responses' `additional_kwargs.reasoning_content`.
  * Supported by:
    * ChatOllama (class level, invocation level TODO)
    * OllamaLLM (TODO)
* Added tests to ensure streaming tool calls is successful (#29129)
* Refactored tests that relied on `extract_reasoning()`
* Myriad docs additions and consistency/typo fixes
* Improved type safety in some spots

Closes #29129
Addresses #31573 and #31700
Supersedes #31701

docs/docs/how_to/callbacks_custom_events.ipynb

@@ -38,11 +38,11 @@
     "\n",
     "\n",
     ":::caution COMPATIBILITY\n",
-    "LangChain cannot automatically propagate configuration, including callbacks necessary for astream_events(), to child runnables if you are running async code in python<=3.10. This is a common reason why you may fail to see events being emitted from custom runnables or tools.\n",
+    "LangChain cannot automatically propagate configuration, including callbacks necessary for astream_events(), to child runnables if you are running async code in `python<=3.10`. This is a common reason why you may fail to see events being emitted from custom runnables or tools.\n",
     "\n",
-    "If you are running python&lt;=3.10, you will need to manually propagate the `RunnableConfig` object to the child runnable in async environments. For an example of how to manually propagate the config, see the implementation of the `bar` RunnableLambda below.\n",
+    "If you are running `python<=3.10`, you will need to manually propagate the `RunnableConfig` object to the child runnable in async environments. For an example of how to manually propagate the config, see the implementation of the `bar` RunnableLambda below.\n",
     "\n",
-    "If you are running python>=3.11, the `RunnableConfig` will automatically propagate to child runnables in async environment. However, it is still a good idea to propagate the `RunnableConfig` manually if your code may run in other Python versions.\n",
+    "If you are running `python>=3.11`, the `RunnableConfig` will automatically propagate to child runnables in async environment. However, it is still a good idea to propagate the `RunnableConfig` manually if your code may run in other Python versions.\n",
     ":::"
    ]
   },

docs/docs/how_to/tool_stream_events.ipynb

@@ -16,15 +16,15 @@
     "\n",
     ":::\n",
     "\n",
-    "If you have [tools](/docs/concepts/tools/) that call [chat models](/docs/concepts/chat_models/), [retrievers](/docs/concepts/retrievers/), or other [runnables](/docs/concepts/runnables/), you may want to access internal events from those runnables or configure them with additional properties. This guide shows you how to manually pass parameters properly so that you can do this using the `astream_events()` method.\n",
+    "If you have [tools](/docs/concepts/tools/) that call [chat models](/docs/concepts/chat_models/), [retrievers](/docs/concepts/retrievers/), or other [runnables](/docs/concepts/runnables/), you may want to access [internal events](https://python.langchain.com/docs/how_to/streaming/#event-reference) from those runnables or configure them with additional properties. This guide shows you how to manually pass parameters properly so that you can do this using the `astream_events()` method.\n",
     "\n",
     ":::caution Compatibility\n",
     "\n",
-    "LangChain cannot automatically propagate configuration, including callbacks necessary for `astream_events()`, to child runnables if you are running `async` code in `python<=3.10`. This is a common reason why you may fail to see events being emitted from custom runnables or tools.\n",
+    "LangChain cannot automatically propagate configuration, including callbacks necessary for `astream_events()`, to child runnables if you are running `async` code in `python<=3.10`. This is a common reason why you may fail to see events being emitted from custom runnables or tools.\n",
     "\n",
-    "If you are running python&lt;=3.10, you will need to manually propagate the `RunnableConfig` object to the child runnable in async environments. For an example of how to manually propagate the config, see the implementation of the `bar` RunnableLambda below.\n",
+    "If you are running `python<=3.10`, you will need to manually propagate the `RunnableConfig` object to the child runnable in async environments. For an example of how to manually propagate the config, see the implementation of the `bar` RunnableLambda below.\n",
     "\n",
-    "If you are running python>=3.11, the `RunnableConfig` will automatically propagate to child runnables in async environment. However, it is still a good idea to propagate the `RunnableConfig` manually if your code may run in older Python versions.\n",
+    "If you are running `python>=3.11`, the `RunnableConfig` will automatically propagate to child runnables in async environment. However, it is still a good idea to propagate the `RunnableConfig` manually if your code may run in older Python versions.\n",
     "\n",
     "This guide also requires `langchain-core>=0.2.16`.\n",
     ":::\n",

docs/docs/how_to/tool_streaming.ipynb

@@ -224,6 +224,13 @@
    "source": [
     "print(type(gathered.tool_calls[0][\"args\"]))"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Note the key difference: accumulating `tool_call_chunks` captures the raw tool arguments as an unparsed string as they are streamed. In contrast, **accumulating** `tool_calls` demonstrates partial parsing by progressively converting the streamed argument string into a valid, usable dictionary at each step of the process."
+   ]
   }
  ],
  "metadata": {