JVM-semantics fixes and small cleanups

- take-last / drop-last return seqs, not vectors: take-last wraps in seq; drop-last
  is the JVM (map (fn [x _] x) coll (drop n coll)) form (lazy, () when empty).
- cycle is lazy ((lazy-seq (concat coll (cycle coll)))) so it no longer counts its
  argument and terminates on a lazy/infinite input.
- fold's foldable-call catch uses :default, matching the rest of jolt-core and
  also catching a raw host condition from a folding primitive.
- alts! rejects non-channel ports with a clear error (put specs / :default are
  unsupported) instead of crashing inside ac-poll!.
- Misc: drop the unreachable second getCause clause; jolt-nth on a string raises
  'nth "index out of bounds" like the vector branch; name the inline fixpoint cap;
  bld-sh-capture rejoins lines with newlines; clarify a couple of comments.

jolt-core/jolt/passes.clj

@@ -23,6 +23,10 @@
                                        reset-escapes! collected-escapes
                                        set-check-mode! take-diags!]]))
 
+;; Cap on inline -> flatten -> scalar-replace -> const-fold iterations. Each pass
+;; sets `dirty` when it rewrote something; the loop stops at a clean pass or here.
+(def ^:private inline-fixpoint-cap 8)
+
 (defn run-passes
   "All passes, in order. The back end applies this to every analyzed form. When
   inlining is enabled for the unit (user code under direct-linking),
@@ -41,7 +45,7 @@
           opt (loop [i 0 n (const-fold node)]
                 (reset! dirty false)
                 (let [n2 (const-fold (scalar-replace (flatten-lets (inline-node n ctx))))]
-                  (if (and @dirty (< i 8))
+                  (if (and @dirty (< i inline-fixpoint-cap))
                     (recur (inc i) n2)
                     n2)))]
       ;; a final const-fold after inference propagates any predicate folded to a