Records the drop-symbol scheme (uniform @drop_<m>_<T> for every
ADT, even no-boxed-children ones; pair+env drop fns for escaping
closures), field_drop_call's per-type dispatch and the three
fall-back cases (Str / Fn / Type::Var), the unchanged Term::Let
emission gates, and the explicit deferral of stack-recursion to
18e's worklist allocator. Also lists the four known-debt items
(stack-recursive drop, closure-typed ADT fields, Type::Var
fields, fn parameters) so 18d's design surface is clear.
Brummel
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