Lands the three load-bearing pieces of ADR-0055 Phase A so later
phases (DiscoveryCandidate, TeachingChainProposal) have a safe
substrate to write into.
- teaching/audit.py: pure, deterministic re-parse of the reviewed
corpus with same gates as the runtime loader but keeps drop
reasons (invalid_json, missing_required_field:*, unsupported_intent,
pack_missing_subject, pack_missing_object, superseded_by:*).
- teaching/provenance.py: typed Provenance(adr_id, source,
review_date, raw); legacy "reviewed" maps to "hand_authored" so
current corpus reports the canonical enum without a file rewrite.
- chat/teaching_grounding._corpus_index honors superseded_by —
active view drops superseded entries while disk preserves history.
- core teaching audit CLI subcommand (--json optional); exits 1 on
any drop so CI catches silent corpus shrinkage from pack swaps.
Observable behaviour unchanged: corpus is 10/10 loaded, all five
core lanes green (smoke 67, cognition 121, runtime 19, teaching 17,
packs 6), cognition eval metrics identical on dev / public /
holdout splits. versor_condition < 1e-6 invariant untouched.
Tests: tests/test_teaching_audit.py — 23 tests covering provenance
parser, real-corpus determinism, every drop-reason path,
supersession semantics, runtime/audit parity, read-only contract.
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