Add AI erasure propagation gates

[Dolpme]

Addresses #2069.

Summary

• Adds an erasure propagation step for AI-derived stores beyond the source database.
• Requires subject-to-artifact lineage, deletion receipts/tombstones, vector/log/dataset/provider reconciliation, training exclusion manifests, backup restore replay, and model-lineage decisions.
• Updates the report template and common pitfalls so reviewers can distinguish source deletion from complete AI erasure.

Validation

• git diff --check
• Frontmatter required-field check across skills/ and roles/
• index.yaml referenced-file existence check
• Markdown fence-balance check for skills/ai-security/ai-data-privacy/SKILL.md
• Target marker check for erasure propagation, lineage, tombstones, provider deletion, training exclusion, backup replay, and model lineage
• Changed-file prompt-injection pattern check

Bounty note: this is intended as an improver-tier contribution under CONTRIBUTING.md; payment details can be provided privately after maintainer acceptance.