fix: LLM mimicking Unicode responses due to forced Unicode conversion of non-ASCII characters. (#32222)

fix: Fix LLM mimicking Unicode responses due to forced Unicode
conversion of non-ASCII characters.

- **Description:** This PR fixes an issue where the LLM would mimic
Unicode responses due to forced Unicode conversion of non-ASCII
characters in tool calls. The fix involves disabling the `ensure_ascii`
flag in `json.dumps()` when converting tool calls to OpenAI format.
- **Issue:** Fixes ↓↓↓
input：
```json
{'role': 'assistant', 'tool_calls': [{'type': 'function', 'id': 'call_nv9trcehdpihr21zj9po19vq', 'function': {'name': 'create_customer', 'arguments': '{"customer_name": "你好啊集团"}'}}]}
```
output:
```json
{'role': 'assistant', 'tool_calls': [{'type': 'function', 'id': 'call_nv9trcehdpihr21zj9po19vq', 'function': {'name': 'create_customer', 'arguments': '{"customer_name": "\\u4f60\\u597d\\u554a\\u96c6\\u56e2"}'}}]}
```
then:
llm will mimic outputting unicode. Unicode's vast number of symbols can
lengthen LLM responses, leading to slower performance.
<img width="686" height="277" alt="image"
src="https://github.com/user-attachments/assets/28f3b007-3964-4455-bee2-68f86ac1906d"
/>

---------

Co-authored-by: Mason Daugherty <github@mdrxy.com>
Co-authored-by: Mason Daugherty <mason@langchain.dev>

libs/partners/fireworks/uv.lock

@@ -653,7 +653,7 @@ wheels = [
 
 [[package]]
 name = "langchain-core"
-version = "0.3.68"
+version = "0.3.72"
 source = { editable = "../../core" }
 dependencies = [
     { name = "jsonpatch" },
@@ -669,7 +669,7 @@ dependencies = [
 requires-dist = [
     { name = "jsonpatch", specifier = ">=1.33,<2.0" },
     { name = "langsmith", specifier = ">=0.3.45" },
-    { name = "packaging", specifier = ">=23.2,<25" },
+    { name = "packaging", specifier = ">=23.2" },
     { name = "pydantic", specifier = ">=2.7.4" },
     { name = "pyyaml", specifier = ">=5.3" },
     { name = "tenacity", specifier = ">=8.1.0,!=8.4.0,<10.0.0" },