Summarize streamed response item logs

[jif-oai]

Why

handle_non_tool_response_item logged the complete decoded ResponseItem at DEBUG. Those values can contain assistant text, reasoning content, and tool payloads that are already stored in the durable rollout, making the SQLite copy both redundant and potentially large or sensitive.

What changed

• Replace the complete item dump with bounded item_type and item_id fields.
• Keep an event-flow breadcrumb for debugging without duplicating item content.
• Leave rollout persistence and tool-call telemetry unchanged.

The item-type match is exhaustive so new response item variants must choose an explicit log label.

Related to #28224.