fix: vertexai default_headers consistency + demo import path

- clients/vertexai/chat_models.py: pass dict(self.uipath_sync_client.headers)
  and dict(self.uipath_async_client.headers) instead of the raw httpx.Headers
  objects, matching the pattern used in clients/anthropic/chat_models.py
- demo.py: import RoutingMode from the public uipath_langchain_client.settings
  API instead of the internal uipath.llm_client.settings.constants path;
  merge with the existing get_default_client_settings import

Author: cosminacho

packages/uipath_langchain_client/demo.py

@@ -17,9 +17,7 @@
 from langchain_core.messages import HumanMessage, SystemMessage
 from langchain_core.tools import tool
 from uipath_langchain_client import get_chat_model, get_embedding_model
-from uipath_langchain_client.settings import get_default_client_settings
-
-from uipath.llm_client.settings.constants import RoutingMode
+from uipath_langchain_client.settings import RoutingMode, get_default_client_settings
 
 
 def demo_basic_chat():

packages/uipath_langchain_client/src/uipath_langchain_client/clients/vertexai/chat_models.py

@@ -41,7 +41,7 @@ def setup_uipath_client(self) -> Self:
             project_id="PLACEHOLDER",
             access_token="PLACEHOLDER",
             base_url=str(self.uipath_sync_client.base_url),
-            default_headers=self.uipath_sync_client.headers,
+            default_headers=dict(self.uipath_sync_client.headers),
             max_retries=0,  # handled by the UiPath client
             http_client=self.uipath_sync_client,
         )
@@ -50,7 +50,7 @@ def setup_uipath_client(self) -> Self:
             project_id="PLACEHOLDER",
             access_token="PLACEHOLDER",
             base_url=str(self.uipath_async_client.base_url),
-            default_headers=self.uipath_async_client.headers,
+            default_headers=dict(self.uipath_async_client.headers),
             max_retries=0,  # handled by the UiPath client
             http_client=self.uipath_async_client,
         )