* content(packs): update relations checksum
* revert transient relations manifest checksum
* content(packs): extend relations lexicon additively
* content(teaching): extend relations chains additively
* content(packs): ratify relations manifest checksum
* test(packs): accept additive relations lemma extension
* test(packs): add relations v1 extension regressions
* fix(tests): align relations extension lemma set
* content(packs): add relations mastery report
* content(packs): drop unused .mastery_report.json sidecar
Language packs do not consume mastery reports — the pattern is from
identity packs (packs/identity/) and has no consumer in language_packs/
loader.py or compiler.py. The added sidecar's self-seal hash also did
not validate against sha256(json.dumps(body, sort_keys=True,
separators=(',', ':'))).
Drop the file. The actual ratification surface for this pack is the
manifest.json lexicon_checksum, which still matches lexicon.jsonl
bytes (verified).