seq fns are lazy by default, like Clojure (LazySeq, not eager-headed)

map/filter/remove/take/drop/concat/take-while/drop-while/mapcat/partition
built an eager-headed cseq: the first element (and the fn application) ran
at construction, so a side-effecting (map f coll) fired f immediately and
(class (map …)) was PersistentList instead of LazySeq. This diverged from
Clojure, which wraps the whole body in lazy-seq. It went unnoticed because
the conformance gate certifies values, not realization — eager and lazy
heads produce identical values — and unit.edn even baked PersistentList in
as expected. test.check's for-all-takes-multiple-expressions (which counts
side effects in a for-all body) exposed it.

Wrap each native producer's result in a lazy-seq node so the body, incl.
the first element, defers until forced — the forced cseq still has eager
heads, so reduce/count/dorun/etc. force on walk and there's no per-element
cost. dedupe's (seq coll) is moved inside its lazy-seq. A jolt LazySeq is
now recognized by coll?/empty, the analyzer's form predicates (a macro can
build its expansion with map), value-host-tags + instance? (LazySeq/ISeq/
Sequential), and reports clojure.lang.LazySeq.

Kept the native Scheme implementations rather than porting Clojure's: a
straight lazy-seq+cons port is 3x slower and Clojure's chunked fast path is
288x slower because jolt's chunk machinery is unoptimized (filed jolt-j9dz);
the wrapped natives are Clojure-lazy at native speed.

+12 corpus rows (laziness at construction, LazySeq type, both JVM-certified).
make test + shakesmoke green, selfhost holds, 0 new divergences.

jolt-core/clojure/core/21-coll.clj

@@ -160,11 +160,14 @@
                             (coll->cells (step (rest s) prev))
                             (coll->cells (cons x (step (rest s) x)))))
                         nil)))))]
-     (let [s (seq coll)]
-       (if s
-         (make-lazy-seq
-           (fn* [] (coll->cells (cons (first s) (step (rest s) (first s))))))
-         ())))))
+     ;; defer (seq coll) into the lazy-seq so a side-effecting source is not
+     ;; realized at construction (dedupe is lazy, like Clojure's).
+     (make-lazy-seq
+       (fn* []
+         (let [s (seq coll)]
+           (if s
+             (coll->cells (cons (first s) (step (rest s) (first s))))
+             nil)))))))
 
 ;; Internal helper for {:keys [...]} destructuring over a seq of k/v pairs —
 ;; canonical Clojure 1.11 shape (core.clj seq-to-map-for-destructuring):