docs(pr-x12): audit findings for hallucinations in PR-X12 docs

Adds .claude/PR-X12-docs-audit.md with full audit table (26 rows),
verified-real anchors, architectural truths, doc-by-doc concentration
ranking, three-tier cleanup recommendations, and scope boundaries.
Recommendations only — no edits to the audited PR-X12 docs themselves.

Author: claude