Store recorded model thoughts

[dannykopping]

Depends on coder/aibridge#168

See https://www.notion.so/coderhq/DRAFT-AI-Bridge-Prompt-Provenance-2ccd579be59280f28021d3baf7472fbe?source=copy_link#2fdd579be59280d494d5efe97b44166d

Store the recorded model thinking/reasoning content to add audit context to tool call invocations.

Acceptance criteria:

• Proto updated to include new message and API
• Migration added to create new table
• aibridgedserver updated to support new API, store records
• Database query to store new records
• Tests added