Compiled global references now deref through the Jolt var cell instead of an
early-bound Janet symbol, so redefining a def/defn is visible to already-compiled
callers (Janet early-binds plain symbols). A global ref analyzes to :op :var
(resolving/creating the cell); a def sets that same cell's root. Because Janet
copies table constants but references functions, we embed memoized getter/setter
closures over the cell rather than the cell itself. This also subsumes the old
named-fn recursion rewrite and the separate ns-intern.
ns-intern now stores the namespace *name* (string) in a var, not the ns table, so
var cells aren't cyclic (required for embedding).
fib(30) compiled ~0.5s (the late-binding cost vs phase 2's direct-linked 0.08s;
direct-linking for hot calls is a later optimization). Suite green; cross-form,
recursion, and context isolation preserved; redefinition now works.
70711b4489