fix: transducers/reduce short-circuit over infinite seqs via reduced

transduce-reduce and core-reduce both called realize-for-iteration, fully
realizing the coll before the reduce loop — so an infinite lazy seq hung before
the reduced short-circuit could fire. (into [] (take 5) (range)) etc. never
terminated.

Add reduce-with-reduced, which steps a lazy seq one cell at a time
(realize-ls/ls cell protocol), checking reduced? after each element so a take/
take-while transducer (or any reducing fn returning reduced) terminates over an
infinite seq. Route transduce-reduce and both core-reduce arities through it;
2-arg reduce now seeds from the first element and reduces the rest lazily.

spec: transducers/short-circuit + reduce/honors-reduced (13 cases).
clojure-test-suite timeouts 7->6, pass 1683->1688. jpm test green.

Fixes jolt-kxb.

test/spec/transducers-spec.janet

@@ -27,3 +27,26 @@
   ["sequence xform"     "[2 3 4]"   "(sequence (map inc) [1 2 3])"]
   ["eduction"           "[2 3 4]"   "(into [] (eduction (map inc) [1 2 3]))"]
   ["completing"         "9"        "(transduce (map inc) (completing +) 0 [1 2 3])"])
+
+# A `take`/`take-while` transducer returns `reduced`, which must short-circuit
+# the reduction so transducing over an INFINITE seq terminates rather than
+# realizing it eagerly.
+(defspec "transducers / short-circuit over infinite seqs"
+  ["into take (range)"        "[0 1 2 3 4]" "(into [] (take 5) (range))"]
+  ["transduce take (range)"   "3"           "(transduce (take 3) + 0 (range))"]
+  ["sequence take (range)"    "[0 1 2 3 4]" "(sequence (take 5) (range))"]
+  ["take-while over (range)"  "[0 1 2]"     "(into [] (take-while (fn [x] (< x 3))) (range))"]
+  ["comp take over (range)"   "[1 3 5]"     "(into [] (comp (filter odd?) (take 3)) (range))"]
+  ["into take iterate"        "[0 1 2 3 4]" "(into [] (take 5) (iterate inc 0))"])
+
+# `reduce` itself honors `reduced`, so a reducing fn that returns `reduced`
+# terminates even over an infinite seq.
+(defspec "reduce / honors reduced"
+  ["reduced short-circuits inf" "105"
+   "(reduce (fn [a x] (if (> a 100) (reduced a) (+ a x))) 0 (range))"]
+  ["reduce take inf"            "10"  "(reduce + (take 5 (range)))"]
+  ["reduce no-init first elem"  "6"   "(reduce + [1 2 3])"]
+  ["reduce no-init single"      "42"  "(reduce + [42])"]
+  ["reduce empty calls f"       "0"   "(reduce + [])"]
+  ["reduce with-init"           "16"  "(reduce + 10 [1 2 3])"]
+  ["reduce reduced immediate"   ":x"  "(reduce (fn [a x] (reduced :x)) :init [1 2 3])"])