core: variadic bit ops, set? covers sorted sets, if rejects extra forms

Three canonical-conformance fixes from the post-shrink batch:

- bit-and/bit-or/bit-xor/bit-and-not get Clojure's variadic arities as
  20-coll shells folding the binary host ops (now __bit-* seams). 2-arg call
  sites still compile to the native janet op via the backend's native-ops
  table. The passes.clj constant-fold table now names the seams — the public
  fns are overlay and don't exist when the compiler loads (this briefly broke
  every compile-mode init).

- core-set? recognizes the :jolt/sorted-set representation (jolt-dpn):
  (set? (sorted-set 1)) was false, and ifn? on sorted sets inherited the bug.

- (if) / (if test) / (if test then else extra) throw in both the analyzer
  and the interpreter — spec 03-special-forms X1, now marked verified.

Suite 4704 -> 4706; bench and the greeter example benchmark are flat.

jolt-core/jolt/analyzer.clj

@@ -133,11 +133,15 @@
 (defn- analyze-special [ctx op items env]
   (case op
     "quote" (quote-node (second items))
-    "if" (if-node (analyze ctx (nth items 1) env)
-                  (analyze ctx (nth items 2) env)
-                  (if (> (count items) 3)
-                    (analyze ctx (nth items 3) env)
-                    (const nil)))
+    "if" (do
+           ;; 2 or 3 argument forms only (spec 03-special-forms X1)
+           (when (or (< (count items) 3) (> (count items) 4))
+             (throw (str "Wrong number of args (" (dec (count items)) ") passed to: if")))
+           (if-node (analyze ctx (nth items 1) env)
+                    (analyze ctx (nth items 2) env)
+                    (if (> (count items) 3)
+                      (analyze ctx (nth items 3) env)
+                      (const nil))))
     "do" (analyze-seq ctx (rest items) env)
     "throw" (throw-node (analyze ctx (nth items 1) env))
     "def" (let [name-sym (nth items 1)]

jolt-core/jolt/passes.clj

@@ -17,7 +17,10 @@
    "<" < ">" > "<=" <= ">=" >= "=" =
    "inc" inc "dec" dec
    "mod" mod "rem" rem "quot" quot
-   "bit-and" bit-and "bit-or" bit-or "bit-xor" bit-xor})
+   ;; the __bit-* seams: the PUBLIC bit fns are 20-coll variadic shells now,
+   ;; which don't exist yet when this ns loads. Folding stays 2-arg (a 3+-arg
+   ;; constant call throws arity inside the fold and is left for runtime).
+   "bit-and" __bit-and "bit-or" __bit-or "bit-xor" __bit-xor})
 
 (defn- const? [n] (= :const (get n :op)))
 (defn- const-num? [n] (and (const? n) (number? (get n :val))))