LLM update + copy changes

* update to Claude sonnet-4.5
* remove copy button on all messages

chat_v2.py

@@ -40,7 +40,7 @@ class LoggedComponents(TypedDict):
 def build_execution_graph() -> CompiledStateGraph:
     llm = ChatBedrock(
         client=boto3.client("bedrock-runtime", region_name="us-east-1"),
-        model=BedrockEndpoints.claude_35_haiku.value
+        model=BedrockEndpoints.claude_45_sonnet.value,
     )
     org_name_recognition = OrganizationIdentifier(llm=llm) # bind the main chat model to the tool
     return create_react_agent(
@@ -60,7 +60,7 @@ def generate_postscript_messages(history: list[gr.ChatMessage]) -> Iterator[gr.C
         if title == search_candid_knowledge_base.name:
             yield gr.ChatMessage(
                 role="assistant",
-                content=html_format_docs_chat(record.metadata.get("documents")),
+                content=html_format_docs_chat(record.metadata.get("documents") or []),
                 metadata={
                     "title": "Source citations",
                 }
@@ -168,7 +168,8 @@ def build_chat_app():
                 height="60vh",
                 type="messages",
                 show_label=False,
-                show_copy_button=True,
+                # show_copy_button=True,
+                show_copy_all_button=True,
                 autoscroll=True,
                 layout="panel",
             )
@@ -236,7 +237,7 @@ def build_app():
     with open(os.path.join(ROOT, "static", "chatStyle.css"), "r", encoding="utf8") as f:
         css_chat = f.read()
 
-    demo = gr.TabbedInterface(
+    return gr.TabbedInterface(
         interface_list=[
             candid_chat,
             feedback
@@ -249,7 +250,6 @@ def build_app():
         theme=gr.themes.Soft(),
         css=css_chat,
     )
-    return demo
 
 
 if __name__ == "__main__":