docs(python): fix KAgentSession import path in kagent-openai README

[anxkhn]

## What

The Session Management example in `python/packages/kagent-openai/README.md`
imports `KAgentSession` from a package path that does not exist:

```python
from kagent.openai.agent._session_service import KAgentSession

There is no agent subpackage under kagent/openai/. The directory
src/kagent/openai/ contains the flat modules _a2a.py, _agent_executor.py,
_event_converter.py, _session_service.py, and a tools/ package. Running
the snippet as written raises:

ModuleNotFoundError: No module named 'kagent.openai.agent'

Fix

Point the import at kagent.openai._session_service, where KAgentSession is
actually defined (_session_service.py) and how the package's own code imports
it (_agent_executor.py uses from ._session_service import KAgentSession):

from kagent.openai._session_service import KAgentSession

Verification

With the kagent-openai package installed:

$ python -c "from kagent.openai.agent._session_service import KAgentSession"
ModuleNotFoundError: No module named 'kagent.openai.agent'

$ python -c "from kagent.openai._session_service import KAgentSession"
# imports cleanly

Docs-only change; no source behavior is affected.

[Copilot]

Pull request overview

Fixes the kagent-openai README’s Session Management example so it imports KAgentSession from the actual module location (kagent.openai._session_service) rather than a non-existent kagent.openai.agent subpackage, preventing a runtime ModuleNotFoundError for users following the docs.

Changes:

• Update the README example import path for KAgentSession to kagent.openai._session_service.

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[supreme-gg-gg]

thanks for the catch!