Foundation type for routing comprehension-reader refusals into the
teaching corridor. Frozen dataclass with sha256 evidence_hash computed
from deterministic canonical bytes (mirrors state.to_canonical_bytes
pattern). Includes SUB_TYPE_FOR_OPERATOR mapping table covering all 13
missing_operator values in the current audit artifact.
Wave 1 only — no runtime mutation, no teaching-store integration, no
admission path. Downstream W2-A/B/C/D type-import from this module.
