openai Decisions: materialize generator-valued instructions and tool outputs #1006

Sub-issue of #1001 (follow-ups from the 2026-10-26 dependency update, #998).

• questions[].instructions now also accepts a list of input parts. _decisions_span_params (integrations/openai/tracing.py:2198) only turns generators into lists for choices / levels and content, so a generator passed as instructions is logged as the generator object.
• One-line fix: add "instructions", and "output" for tool outputs, to the nested-field lists.