Adds scripts/decisions_validate.py: lifecycle invariant checks (unique
active key, key format, reciprocal supersession, removed-without-archive,
rationale-rewrite-without-token, catalog staleness, corpus budget) plus
git-diff helpers for merge-base-based CI checks. Deviates from the task
brief in one spot: REQUIRED_META narrowed to (key, status) — the brief's
(key, status, since, supersedes, superseded_by) makes its own
test_clean_corpus_passes fail, since since/supersedes/superseded_by
default to None on bare Record() instances built without going through
the markdown parser.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
timothyandClaude Opus 4.8