feat(wiki): add multimodal incremental and eval helpers

[MarinaMackay]

Summary

Part 4d of the multimodal repository knowledge stack.

This slice adds incremental update planning and MMWiki-style evaluation helpers.

Testing

python -m pytest test/wiki/test_media_incremental.py test/wiki/test_media_eval.py

[fishmingyu]

Thank you for the incremental/evaluation slice. To keep the upstream review focused, I split the two independent commits: the incremental planner is now upstream as sysevol-ai#673 with your authorship preserved, while the MMWiki evaluation helper remains a local dependent follow-up. The maintainer pass updated trusted-artifact normalization, handles missing facts, bounds iterators, and validates incremental provenance. Local incremental-stack verification: 441 passed.