Brummel
9973546e3b
Sharpen the feature-acceptance criterion (DESIGN.md, mirrored in the
brainstorm gate) with a third conjunctive-necessary clause: a feature
reintroduces no bug class the core constraint exists to eliminate.
Criterion 1 ("an LLM reaches for it") does not discriminate — an LLM
reaches for every construct native to its imperative training
distribution, so utility alone would launder the imperative paradigm
back in one construct at a time. Clause 3 is the discriminator; a
documentation note is not a reshape (the gate is whether the wrong
code fails to typecheck).
Record the decided iteration story as a P1 milestone: structural
recursion permitted (total-by-construction under Decision 10's
acyclic-ADT invariant) + named loop/recur as the only other
repetition + tail-app retired. Discharges fieldtest finding F1 without
introducing an imperative construct; closes the residual "forgot to
mark tail" trap completely; unifies with Decision 10 (acyclic values
AND acyclic implicit call graph). Supersedes the "while-loops legal"
scope bullet of the Stateful-islands milestone, which is amended for
internal consistency. The escaping-state path (ref/MutArray/Stateful)
is unaffected and stays in Stateful-islands.