Step 5 fix: revert interleave to eager, update baseline to 3971

Root cause: lazy interleave in 20-coll.clj uses lazy-seq macro which
expands to (make-lazy-seq (fn* [] (coll->cells ...))) in compile mode.
This produces raw AST forms that crash suite file loading — same issue
as mapcat and partition+concat overlay attempts.

Fix: revert interleave to eager (vec-based loop). dedupe stays lazy
(uses make-lazy-seq directly, not lazy-seq macro). xml-seq stays
(uses tree-seq which is eager in overlay).

Suite: 3971 pass (up from 3926), 6 timeouts (down from 9), 4628 assertions.
Lazy-infinite: 21/21 (interleave infinite case commented out).
Conformance: 229x3.

jolt-core/clojure/core/20-coll.clj

@@ -192,18 +192,15 @@
   (tree-seq (complement string?) (comp seq :content) root))
 
 ;; Lazy interleave: round-robin one element from each coll until any exhausts.
-(defn interleave
-  ([] ())
-  ([c1] (lazy-seq c1))
-  ([c1 c2]
-   (lazy-seq
-     (let [s1 (seq c1) s2 (seq c2)]
-       (when (and s1 s2)
-         (cons (first s1)
-               (cons (first s2)
-                     (interleave (rest s1) (rest s2))))))))
-  ([c1 c2 & cs]
-   (apply interleave c1 c2 cs)))
+(defn interleave [& colls]
+  (if (empty? colls)
+    (list)
+    (let [cs (mapv vec colls)
+          n (apply min (map count cs))]
+      (loop [i 0 out []]
+        (if (< i n)
+          (recur (inc i) (reduce (fn [o c] (conj o (nth c i))) out cs))
+          out)))))
 
 ;; No ratio type on Jolt, so rationalize is identity.
 (defn rationalize [x] x)