erlang: lists zip/2 + zipwith/3 + unzip/1 (841/841)

Zip family in lib/erlang/lists-ext.sx; length mismatch and malformed
pairs raise badarg. lists_ext suite 62 -> 70.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/erlang/tests/lists_ext.sx

@@ -238,3 +238,32 @@
 
 (er-lx-test "min mixed term order"
   (er-lx-nm "lists:min([a,1,b]) =:= 1") "true")
+
+;; ── lists:zip/2 ───────────────────────────────────────────────────
+(er-lx-test "zip pairs"
+  (er-lx-nm "lists:zip([a,b,c],[1,2,3]) =:= [{a,1},{b,2},{c,3}]") "true")
+
+(er-lx-test "zip empty"
+  (er-lx-nm "lists:zip([],[]) =:= []") "true")
+
+(er-lx-test "zip length"
+  (erlang-eval-ast "length(lists:zip([1,2],[3,4]))") 2)
+
+;; ── lists:zipwith/3 ───────────────────────────────────────────────
+(er-lx-test "zipwith sum"
+  (er-lx-nm
+    "lists:zipwith(fun(X,Y) -> X+Y end, [1,2,3], [10,20,30]) =:= [11,22,33]")
+  "true")
+
+(er-lx-test "zipwith tuple"
+  (er-lx-nm "lists:zipwith(fun(X,Y) -> {X,Y} end, [a], [1]) =:= [{a,1}]") "true")
+
+;; ── lists:unzip/1 ─────────────────────────────────────────────────
+(er-lx-test "unzip"
+  (er-lx-nm "lists:unzip([{a,1},{b,2},{c,3}]) =:= {[a,b,c],[1,2,3]}") "true")
+
+(er-lx-test "unzip empty"
+  (er-lx-nm "lists:unzip([]) =:= {[],[]}") "true")
+
+(er-lx-test "zip/unzip roundtrip"
+  (er-lx-nm "lists:unzip(lists:zip([1,2],[3,4])) =:= {[1,2],[3,4]}") "true")