Schema-only module defining ReasoningStep / ReasoningTrace with
byte-identical canonical serialization and sha256 trace_id derivation.
Replay-equivalence is enforced by:
- sorted-key JSON, no whitespace, ensure_ascii=False, allow_nan=False
- recursive rejection of float values in payloads (replay hazard)
- step_index monotonicity from 0
- empty trace rejected
- Literal-checked step_kind across all eight Tier 1+2 kinds
No runtime hook. No import from chat/field/generate/algebra.
Downstream (W1 ShapeProposal, W2 decomposer) consume this schema.
Tests: 12 new, full teaching suite green (17 passed).
