docs: preserve historical decision revalidation

[nothingnesses]

Summary

• Preserve 100 original decision clusters and 14 follow-up dispositions in one sanitised report.
• Distinguish shipped behaviour, selected future directions and unresolved historical proposals.
• Keep raw sessions, inventories and temporary analyses outside Git.

Dependency

This PR depends on #7 and initially targets its branch. Merge #7 first. Retarget this PR to main after the parent merge. Check the resulting diff and CI before merge.

Verification

• Host just ci passed after commit a64d6c27a2171b5fe311f7ab05f1d8cbe8aeff2d.
• Independent review found one low-impact error in the evidence guide. The scoped correction passed focused verification.
• Report checks passed for all 114 dispositions, historical references, ASCII, size, tables and local links.

Authority

The report records decisions. It authorises no implementation, issue creation, deletion, publication, merge or work-completion change. Future work requires separate approval.