Fix tool call index assignment in Delta class

- Update tool call index logic to assign sequential indices when missing
- Replace default index=0 behavior with proper sequential assignment
- Maintain OpenAI API compatibility with correct tool call indexing
- Preserve existing behavior for tool calls with explicit indices
- Universal fix benefiting all providers using Delta class

Author: timelfrink

litellm/types/utils.py

@@ -754,10 +754,12 @@ def __init__(
             self.function_call = function_call
         if tool_calls is not None and isinstance(tool_calls, list):
             self.tool_calls = []
+            current_index = 0
             for tool_call in tool_calls:
                 if isinstance(tool_call, dict):
                     if tool_call.get("index", None) is None:
-                        tool_call["index"] = 0
+                        tool_call["index"] = current_index
+                        current_index += 1
                     self.tool_calls.append(ChatCompletionDeltaToolCall(**tool_call))
                 elif isinstance(tool_call, ChatCompletionDeltaToolCall):
                     self.tool_calls.append(tool_call)