First shippable milestone on the Stateful-islands roadmap path:
sealed-by-construction local mutable bindings in fn bodies, with
no ref-types, no effect handlers, no escape. Lowers entirely to
LLVM allocas with statically-bounded lifetime; fn signatures stay
pure (no !Mut effect leakage).
Three iterations: mut.1 (schema + surface), mut.2 (typecheck +
diagnostics), mut.3 (codegen + e2e). Var element types restricted
to Int/Float/Bool/Unit (non-RC-managed scalars) in this milestone;
Str/ADT/fn-value vars deferred.
Grounding-check PASS on iteration mut.1 assumptions: Term enum
extension is gated by design_schema_drift, round-trip by
ailang-surface round_trip auto-discovery, DESIGN.md amendment by
the same drift test, schema_coverage forces a corpus fixture.
Brummel
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