## Summary
Plumbs the Responses output item id (added as `ToolUsageRecord.ItemID` in #26855) through to the database, captured independently of the `provider_tool_call_id` correlation key. Hosted tools (`web_search_call`, etc.) only have an item id; agentic tools have both.
`provider_item_id` is specific to the OpenAI Responses API; it stays empty for chat completions and Anthropic messages, which have no separate item id.
## Changes
- Migration `000534`: nullable `provider_item_id` column on `aibridge_tool_usages`.
- Proto: `item_id` field 11 on `RecordToolUsageRequest`.
- Server handler: persists `provider_item_id` and adds it to structured logging.
- Translator: maps `ToolUsageRecord.ItemID` to the proto field.
## Tests
- `TestRecordToolUsageProviderItemID`: real-database round-trip asserting `provider_item_id` persists for both hosted and agentic tools, independently of `provider_tool_call_id`.
Stacked on #26855. Linear: AIGOV-96
---
_This PR was produced by opencode (agent) using the_ _`anthropic/claude-opus-4-8`_ _model, under human direction and review._
Danny Kopping
dd216b96fe