- Add [UNTRUSTED CONTENT] markers for external-provenance memories in
extraction prompts (provenance == 2)
- Parallelize extract_batch using futures::future::join_all instead of
sequential processing
- Consolidate duplicate FullMockGateway/TestGateway into shared
test_helpers::MockGateway with configurable inference support
Closes#120
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>