data.priority-map: deftype interop fixes (rseq, arity-overload, empty, Sorted)

data.priority-map's whole suite passes (4/4). It leans on deftype/collection
interop jolt got wrong; four general fixes:

- rseq dispatches to a deftype's clojure.lang.Reversible.rseq method instead of
  always demanding a vector/sorted-coll (natives-seq.ss).
- a deftype method declared at two arities from two interfaces now dispatches by
  arity: the priority-map has seq[this] (Seqable) and seq[this ascending]
  (Sorted), so (.seq pm false) must reach the 2-arg one. find-method-any-protocol
  now matches the call's arg count via procedure-arity-mask, and a deftype's own
  declared method wins over the generic collection interop in dot-forms.
- (empty x) on a deftype/record with its own empty method uses it rather than
  returning {} (jolt.host/jrec-method? gate in clojure.core/empty).
- clojure.lang.Sorted (comparator / entryKey / seqFrom) works on jolt's
  sorted-map/set, so subseq/rsubseq run — including the priority-map delegating
  .comparator to its backing sorted-map (dot-forms.ss + host-static.ss).

Listed in docs/libraries.md + the site. One re-mint (clojure.core/empty);
everything else runtime. make test green (0 new divergences), shakesmoke
byte-identical.

host/chez/natives-seq.ss

@@ -224,9 +224,14 @@
 
 ;; rseq: vectors + sorted colls only (Clojure), the reverse of the ascending seq.
 (define (jolt-rseq coll)
-  (if (or (pvec? coll) (htable-sorted? coll))
-      (list->cseq (reverse (seq->list (jolt-seq coll))))
-      (jolt-throw (jolt-ex-info "rseq requires a vector or sorted collection" (jolt-hash-map)))))
+  (cond
+    ((or (pvec? coll) (htable-sorted? coll))
+     (list->cseq (reverse (seq->list (jolt-seq coll)))))
+    ;; a deftype/record implementing clojure.lang.Reversible (rseq) — e.g.
+    ;; data.priority-map — drives rseq through its own method.
+    ((and (jrec? coll) (find-method-any-protocol (jrec-tag coll) "rseq"))
+     => (lambda (f) (jolt-invoke f coll)))
+    (else (jolt-throw (jolt-ex-info "rseq requires a vector or sorted collection" (jolt-hash-map))))))
 (def-var! "clojure.core" "rseq" jolt-rseq)
 
 ;; clojure.core/unchecked-* — host-defined wrapping (Java long) arithmetic from