[opentelemetry-instrumentation-google-genai] Use wrapt to monkey patch instead of functools.wraps. Clarify readme tool calling section.

[DylanRussell]

Description

Use wrapt to monkey patch (https://pypi.org/project/wrapt/) instead of functools.wraps.. I think this is a good best practice, I see openinference's instrumentation uses this, and a bunch of instrumentation in contrib..

I also updated the README to correctly describe when we generate an execute_tool span (we do it when automatic function calling is enabled only..)..

Fixes # (issue)

• [ x] Bug fix (non-breaking change which fixes an issue)

How has this been tested?

Unit tests

Checklist

See CONTRIBUTING.md
for the style guide, changelog guidance, and more.

• [x ] Followed the style guidelines of this project
• [ x] Changelog updated if the change requires an entry
• [x ] Unit tests added
• [ x] Documentation updated

[Copilot]

Pull request overview

This PR updates the Google GenAI instrumentation to use wrapt’s wrap_function_wrapper for monkey-patching SDK methods (instead of functools.wraps + direct assignment), and adjusts the README to clarify how tool-call spans are emitted when automatic function calling is enabled.

Changes:

• Switch Models/AsyncModels patching to wrapt.wrap_function_wrapper wrappers.
• Clarify README limitation text around execute_tool spans and when tool calls are traced.
• Add wrapt as a package dependency and record the change via a towncrier fragment (and remove the corresponding TODO).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
instrumentation/opentelemetry-instrumentation-google-genai/TODOS.md	Removes the “adopt wrapt” TODO now that it’s implemented.
instrumentation/opentelemetry-instrumentation-google-genai/src/opentelemetry/instrumentation/google_genai/generate_content.py	Reworks patching/wrappers to use wrap_function_wrapper and adjusts wrapper signatures/flow.
instrumentation/opentelemetry-instrumentation-google-genai/README.rst	Updates limitation text describing tool-call span behavior.
instrumentation/opentelemetry-instrumentation-google-genai/pyproject.toml	Adds wrapt dependency.
instrumentation/opentelemetry-instrumentation-google-genai/.changelog/151.changed	Adds a changelog fragment for the wrapt monkey-patching change.

Comments suppressed due to low confidence (1)

instrumentation/opentelemetry-instrumentation-google-genai/src/opentelemetry/instrumentation/google_genai/generate_content.py:683

• In the async streaming wrapper, extra attributes from context are applied before _apply_request_attributes(...), which is inconsistent with the sync wrappers. Applying extras last is safer because it lets caller-provided extra attrs override defaults in case of key collisions.

            invocation.attributes.update(
                _get_extra_generate_content_attributes()
            )
            _apply_request_attributes(
                wrapped_config,