Improve AI data deletion propagation gates

[DENGXUELIN]

/claim #1382

Summary

• Adds AI data deletion propagation gates to ai-data-privacy.
• Requires source-to-derived mapping across primary records, RAG sources, embeddings, vector indexes, logs, training snapshots, model artifacts, analytics exports, backups, provider retention, and legal holds.
• Adds benign and vulnerable JSON fixtures for complete deletion propagation versus primary-record-only deletion that leaves AI-derived data retrievable.

Validation

• git diff --check origin/main...HEAD
• JSON parse check for both fixtures
• Markdown fence-balance and required-marker checks
• Added-line sensitive-pattern scan
• git merge-tree --write-tree origin/main HEAD matched HEAD^{tree}