apl: ? roll/random + apl-rng-seed! (+4 tests)

apl-rng-state global mutable LCG.
apl-rng-seed! for deterministic tests.
apl-rng-next! advances state.
apl-roll: monadic ?N returns scalar in 1..N (apl-io-relative).

apl-monadic-fn dispatches "?" → apl-roll.

apl-run "?10" → 8 (with seed 42)
apl-run "?100" → in 1..100

lib/apl/tests/pipeline.sx

@@ -359,3 +359,24 @@
   "inline-assign in dfn: f ← {x + x ← ⍵} ⋄ f 8 → 16"
   (mkrv (apl-run "f ← {x + x ← ⍵} ⋄ f 8"))
   (list 16))
+
+(begin (apl-rng-seed! 42) nil)
+
+(apl-test
+  "?10 with seed 42 → 8 (deterministic)"
+  (mkrv (apl-run "?10"))
+  (list 8))
+
+(apl-test "?10 next call → 5" (mkrv (apl-run "?10")) (list 5))
+
+(apl-test
+  "?100 stays in range"
+  (let ((v (first (mkrv (apl-run "?100"))))) (and (>= v 1) (<= v 100)))
+  true)
+
+(begin (apl-rng-seed! 42) nil)
+
+(apl-test
+  "?10 with re-seed 42 → 8 (reproducible)"
+  (mkrv (apl-run "?10"))
+  (list 8))