fix: replace nonexistent trace_tool_response with trace_merged_tool_calls in ADK patch

[MaxwellCalkin]

Summary

Fix Google ADK instrumentation error on startup:

Could not wrap google.adk.telemetry.trace_tool_response: module 'google.adk.telemetry' has no attribute 'trace_tool_response'

Fixes #1257.

Problem

google.adk.telemetry.trace_tool_response does not exist in any supported version of google-adk (1.4.1+). The function was renamed to trace_merged_tool_calls with a different signature:

# Old (nonexistent):
trace_tool_response(invocation_context, event_id, function_response_event)

# Current:
trace_merged_tool_calls(response_event_id, function_response_event)

Additionally, _adk_trace_tool_call_wrapper incorrectly extracts args[0] as the tool arguments dict when it is actually the tool object. The current trace_tool_call signature is:

trace_tool_call(tool: BaseTool, args: dict, function_response_event: Event)

Changes

• Replace _adk_trace_tool_response_wrapper with _adk_trace_merged_tool_calls_wrapper matching the trace_merged_tool_calls(response_event_id, function_response_event) signature
• Fix _adk_trace_tool_call_wrapper to correctly extract the tool object from args[0] and tool arguments from args[1]
• Update patch_adk() to wrap trace_merged_tool_calls instead of trace_tool_response

Test plan

• Verify no more "Could not wrap trace_tool_response" warning on startup with google-adk >= 1.4.1
• Verify tool call and merged tool call attributes are correctly set on spans
• Verify existing ADK instrumentation continues to work (agent spans, LLM spans, tool spans)

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.
To continue using code reviews, you can upgrade your account or add credits to your account and enable them for code reviews in your settings.

[themavik]

This PR fixes the ADK patch to use trace_merged_tool_calls instead of the nonexistent trace_tool_response, and updates the trace_tool_call wrapper for the new signature.

Done well: The wrapper correctly extracts tool and tool_args from the new trace_tool_call(tool, args, function_response_event) signature. Adding tool_name to span attributes when tool has a name is useful. The trace_merged_tool_calls wrapper maps response_event_id and function_response_event from the new signature. The try/except around model_dump_json with fallback to less-than-serializable is a good defensive touch.

Suggestion: The old trace_tool_response took invocation_context, event_id, function_response_event. The new trace_merged_tool_calls drops invocation_id. If that was used for correlation elsewhere, consider whether response_event_id or another field can fill that role. Also worth verifying the ADK version that introduced trace_merged_tool_calls so the patch is version-gated or documented.