Python: fix sequential workflow sample output handling

[he-yufeng]

Summary

• update the sequential workflow sample to avoid treating streaming output chunks as a final conversation list
• use output_from=all so both participant responses are visible
• print the initial user prompt plus each agent response message from the non-streaming run result

Fixes #5975

To verify

• uv run python -m py_compile samples/03-workflows/orchestrations/sequential_agents.py
• uv run ruff check samples/03-workflows/orchestrations/sequential_agents.py
• uv run pyright samples/03-workflows/orchestrations/sequential_agents.py
• uv run pytest packages/orchestrations/tests/test_sequential.py packages/orchestrations/tests/test_orchestration_intermediate_vs_terminal.py -q -p no:cacheprovider

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Updates the Python sequential workflow sample to correctly handle sequential workflow outputs by using non-streaming results and printing both agents’ visible responses.

Changes:

• Switches the sample from streaming collection to a single non-streaming run() result.
• Configures the workflow to emit outputs from all participants (output_from="all").
• Builds and prints a combined conversation containing the initial user prompt plus each agent’s response messages.

[moonbox3]

Thanks for the fixes.