fix: guard None text in text_message_output and add output guardrail count to RunErrorDetails

[zhoufengen]

Summary

Two small, related fixes in the SDK's output-handling utilities:

1. ItemHelpers.text_message_output — guard against None text

extract_text (the sibling method in the same class) already applies an or "" guard with an explicit comment explaining that provider gateways (e.g. LiteLLM) and model_construct paths during streaming can surface None for ResponseOutputText.text. text_message_output had the same concatenation loop without the guard, so the same TypeError: can only concatenate str (not "NoneType") to str could fire through text_message_outputs and agent.py's text_output path.

Fix: text += item.text or ""

2. pretty_print_run_error_details — include output guardrail count

pretty_print_result and pretty_print_run_result_streaming both report input_guardrail_results and output_guardrail_results. pretty_print_run_error_details reported only the input count, so RunErrorDetails.__str__() silently omitted output guardrail results — misleading when an output guardrail is the reason the run failed.

Fix: add the missing output_guardrail_results line.

Test plan

New file tests/utils/test_pretty_print_and_items.py (5 tests):

• test_text_message_output_returns_empty_string_for_none_text — reproduces the TypeError on the old code via model_construct
• test_text_message_output_returns_text_normally — normal path still works
• test_text_message_outputs_handles_none_text_across_items — multi-item list with a None entry
• test_pretty_print_run_error_details_includes_output_guardrail_count — asserts both counts appear
• test_pretty_print_run_error_details_zero_output_guardrails — zero case

Updated inline snapshot in tests/test_pretty_print.py::test_pretty_run_error_details.

uv run pytest tests/utils/test_pretty_print_and_items.py tests/test_pretty_print.py -v

Full verification stack:

• make format — no changes
• make lint — all checks passed
• make typecheck — mypy: no issues (767 files), pyright: 0 errors
• make tests (parallel + serial) — all passed

Issue number

N/A (no existing issue; both are small, self-contained defects).

Checks

• I've added new tests (if relevant)
• I've added/updated the relevant documentation
• I've run make lint and make format
• I've made sure tests pass