fix(gemini): group parallel function_response parts in a single Content object

When Gemini makes N parallel tool calls, the API requires all N function_response parts in one Content object. Previously each tool result created a separate Content, causing 400 INVALID_ARGUMENT errors. Merge consecutive function_response parts into the existing Content instead of appending new ones.

lib/crewai/src/crewai/llms/providers/gemini/completion.py

@@ -634,9 +634,25 @@ class GeminiCompletion(BaseLLM):
                 function_response_part = types.Part.from_function_response(
                     name=tool_name, response=response_data
                 )
-                contents.append(
-                    types.Content(role="user", parts=[function_response_part])
-                )
+                # Gemini requires all parallel function responses in a single
+                # Content object.  When the previous Content already holds
+                # function_response parts, merge into it instead of creating
+                # a new Content.
+                if (
+                    contents
+                    and contents[-1].role == "user"
+                    and contents[-1].parts
+                    and all(
+                        hasattr(p, "function_response")
+                        and p.function_response is not None
+                        for p in contents[-1].parts
+                    )
+                ):
+                    contents[-1].parts.append(function_response_part)
+                else:
+                    contents.append(
+                        types.Content(role="user", parts=[function_response_part])
+                    )
             elif role == "assistant" and message.get("tool_calls"):
                 raw_parts: list[Any] | None = message.get("raw_tool_call_parts")
                 if raw_parts and all(isinstance(p, types.Part) for p in raw_parts):