Implements ADR-0181 PR-6 (eval-plan §4): teachers label or align; they never
define the substrate and never fold embeddings into the versor path.
- sensorium/audio/teachers.py:
- TeacherHint: typed, versioned, checksummed annotation (no raw embeddings).
- AudioTeacher protocol (pure on the signal).
- attach_teacher_hints: the ONLY admission path — appends content.* anchors to
the IR's content_anchors (immutable, recomputes ir_sha256). content.* is not
an operator key, so compile_events skips it: versor + projection_sha256 stay
byte-identical; only the ir leg of the merge_key moves (evidence recorded).
- KNOWN_TEACHER_LANES (whisper/nemo/clap/encodec): declared + gated behind
optional extras; load_teacher import-guards and fails loudly (never a silent
fallback). StubTranscriptTeacher is the deterministic reference instance.
- parser.py: extract _ir_payload + ir_sha256_of (DRY single source of truth for
ir_sha256; byte-identical to parse() output — regression-guarded).
- pyproject.toml: audio-whisper/nemo/clap/encodec optional extras (never
runtime-required).
16 failable proof tests in tests/test_audio_teachers.py. Load-bearing:
test_teacher_hint_does_not_change_versor. Mutation-verified — giving a teacher
anchor an operator event_type (folding it into the versor) fails the
versor-invariance proof; reverted, all pass.
Additive only (ADR-0013): no core layer touched. Audio suite 57/57; eval-gate
ir_sha256 pins unchanged by the parser refactor; architectural invariants 40/40.
Real model adapters are deferred until extras+weights are present; this PR ships
the policy, the typed-hint contract, and the shadow-only guarantee.
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