Add Axiom graph adapter surfaces and simulate.rules_by_ref@1 (NZ v0, G1)

changelog.d/axiom-graph-adapter.added.md

@@ -0,0 +1,21 @@
+Prepare the Axiom adapter for graph nodes. `NZ_SCHEMA` declares persons in
+households and families. `AxiomEngine(nesting=NZ_NESTING)` refuses a family
+whose members sit in two households, from the person memberships alone, and an
+explicit `{group}_{parent}_id` column must agree with those memberships. A
+`periods={label: AxiomPeriod(...)}` mapping resolves labels such as `"2026-27"`
+to explicit `tax_year` bounds and refuses any label it does not map.
+
+`output_dtypes="graph"` casts outputs to graph-ownable dtypes without loss:
+judgments become int64 codes, integers int64, decimals float64. It refuses text
+and date outputs. The default output stays as before.
+
+`axiom_engine_ref` builds an `engine_ref` from the engine commit and wheel
+digest, the RuleSpec commit, the module and whole-root content digests, and the
+adapter configuration, so a RuleSpec edit re-keys every node that names it. It
+also pins the adapter, which then refuses to compile from a root whose bytes
+have moved. A git-checkout root must hold exactly the declared commit.
+`assert_no_relations` refuses relation-bearing modules.
+
+The new `simulate.rules_by_ref@1` kernel (`microcosm.frame.rules_kernels`) runs
+several rules engines in one graph run. It routes each node to the adapter its
+`engine_ref` names, with the `simulate.rules@1` contract unchanged.