deftype binds the type name as a VAR (the make-deftype-ctor closure), but (P. 5)
lowers to (host-new "P"), which only checked class-ctors-tbl -> "No constructor".
Fall back to resolving the class name as a var in the current ns / clojure.core
and invoking it — so (P. args) constructs the same jrec as the ->P factory, and
protocol method dispatch (.m / .-field) over it works.
zero-Janet 2685->2688 (no-constructor 5->2); prelude floor bumped to 2641 (the
delay batch's run). Self-host + Janet gates + JVM cert green.
jolt-cf1q.7
60b4bae105