Phase 2.2, structure only (no inference rule — modus_ponens is 2.3). Translates a
Proof into a SemanticSymbolicBindingGraph; the ADR-0203 acyclicity guard + ADR-0132
referential integrity fire at construction.
- generate/proof_chain/model.py: the one canonical proof input shape (ProofNode/Proof
+ proof_from_premises desugaring of the corpus premises/conclusion shape).
- generate/proof_chain/builder.py: build_proof_graph — node→symbol+equation;
canonical_key→rhs_canonical, depends_on→dependencies, rule→operation_kind;
premises = empty-deps/op="premise"; unit_proof=PROOF_NO_UNIT, admissibility="pending";
conclusion tracked as conclusion_symbol_id.
- tests: 9 — valid DAG (PC-MP-001 desugared) + multistep construct; PC-CYCLE-001
refuses THROUGH the real builder (circular_dependency); canonical_key round-trips
byte-identical + equivalent formulas share rhs_canonical; admissibility-dispatch
confirmation; self/dangling refusals; out-of-regime node refuses. Mutation-verified
(drop dep-wiring -> cycle admitted -> test fails).
Admissibility dispatch confirmed graceful on proof operation_kinds: unknown kinds
-> AdmissibilityError(unknown_operation), unitless deps -> unit_unbound; NEVER
misroutes into _check_additive. Named 2.3 constraint: check_admissibility runs
_resolve_dep_units before dispatch, so modus_ponens must bypass unit-resolution.
Open items named for 2.3 (ADR-0204): conclusion typing (BoundUnknown revisit),
semantic_role="unknown" (closed vocab has no "proposition"), unit_proof sentinel.
Additive (first consumer; math lane untouched). Full binding-graph surface green;
smoke 67. Honesty boundary: through 2.3, sound over declared atoms, not grounded in input.
