Fold type predicates on proven types (jolt-wcw) (#129)

When the collection-type inference proves an argument's type, number?/
string?/keyword?/record?/nil?/some? fold to a compile-time boolean. A
const-fold now runs after inference so a folded predicate propagates and
collapses any if it gates to the taken branch.

Sound by construction: only a provable answer folds, and only when the
argument is side-effect-free (a const or local) so dropping its evaluation
is a no-op. Unknown types (:any/:truthy) and impure args keep the call.
vector?/set?/map? are left out — the :vec tag conflates a real vector with
a range/seq, so vector? could be wrong.

50M-iter loop, same shape isolated with a carry-only control: number? call+
branch 5080ms, predicate folded 1365ms — matching the 1417ms control floor,
so the 3.7x is entirely the eliminated call+branch.

Co-authored-by: Yogthos <yogthos@gmail.com>

jolt-core/jolt/passes.clj

@@ -39,5 +39,7 @@
                   (if (and @dirty (< i 8))
                     (recur (inc i) n2)
                     n2)))]
-      (run-inference opt))
+      ;; a final const-fold after inference propagates any predicate folded to a
+      ;; constant (jolt-wcw), collapsing the `if` it gates to the taken branch.
+      (const-fold (run-inference opt)))
     (const-fold node)))