Five type predicates (number?, string?, list?, boolean?, symbol?).
New tests/metacircular.sx: m-eval defined in Kernel walks expressions
itself, recursing on applicative-call args and delegating to host
eval only for operatives and symbol lookup. 14 demo tests.
The demo surfaced a real bug: map/filter/reduce called kernel-combine
on applicative head-vals directly, which re-evaluates already-
evaluated element values; nested-list elements crashed. Fix: extracted
knl-apply-op (unwrap-applicative-or-pass-through) and use it in all
three combinators before kernel-combine. Mirrors apply's approach.
Added knl-apply-op as a proposed entry in the reflective combiner.sx
API. 322 tests total.