[walcz-de]

Description

The PII middleware scans the text of every message, but images, audio, video and files reach the backend unchecked. For an egress policy on cloud-proxy models ("nothing sensitive leaves the box") that is a gap: a photographed invoice or an attached PDF goes to the provider without any check.

This adds pii.block_unscanned_media. While PII is enabled for a model and the option is set, a request carrying such content is rejected with the usual 400 pii_blocked response and an audit event (pattern __unscanned_media__) before any detector runs. Adapters report unscanned content through a new optional Adapter.Unscanned:

• OpenAI chat: non-text content blocks (image_url, input_audio, file, …)
• Anthropic messages: image and document blocks (tool blocks stay allowed)
• Ollama chat: images

Off by default; existing configurations behave as before. The option is also exposed in the model editor (config meta registry).

Notes for Reviewers

• Middleware specs: blocks and records an event; blocks without detectors; text-only passes; option off passes; PII disabled passes. Adapter specs for all three shapes with text-only negatives. A mutation (block disabled) turns the middleware specs red.
• If feat(pii): apply PII middleware to the Open Responses API #12708 (PII on /v1/responses) lands, a follow-up commit there reports input_image/input_file/input_audio the same way (already pushed to that branch, it carries this commit as its base).
• Not run: golangci-lint, e2e suites.

Signed commits

• Yes, I signed my commits.
• Documentation updated (docs/content/) for user-facing changes, or not applicable