test: fold ported-clojure batteries into spec

Mine the remaining integration 'ported Clojure' batteries into the spec layer
and delete them (clojure-atom/control/for/logic/macros, core, logic). A broad
function-coverage diff confirmed they exercised no clojure.core fn the spec
lacked; their distinctive value was the truthiness/boolean contract, now
captured in a dedicated spec.

New/expanded spec coverage:
- spec/truthiness-spec: only nil/false are falsy (0, "", [], {}, #{} are truthy);
  not / and / or return-value & short-circuit semantics; if-not/when-not/boolean
- assert (exceptions-spec), get-validator (state-spec)

Layout now: spec 23 files / 732 cases; integration trimmed to 10 genuine
cross-cutting batteries (conformance, SCI bootstrap/runtime, jank, compile-mode,
api, namespace, bootstrap, features, systematic-coverage). conformance 218/218,
jpm test green.

test/spec/state-spec.janet

@@ -21,7 +21,8 @@
   ["add-watch fires"    "1"      "(let [a (atom 0) seen (atom 0)] (add-watch a :k (fn [k r o n] (reset! seen 1))) (reset! a 5) @seen)"]
   ["remove-watch"       "0"      "(let [a (atom 0) seen (atom 0)] (add-watch a :k (fn [k r o n] (swap! seen inc))) (remove-watch a :k) (reset! a 5) @seen)"]
   ["set-validator! ok"  "5"      "(let [a (atom 0)] (set-validator! a number?) (reset! a 5) @a)"]
-  ["set-validator! rejects" :throws "(let [a (atom 0)] (set-validator! a pos?) (reset! a -1))"])
+  ["set-validator! rejects" :throws "(let [a (atom 0)] (set-validator! a pos?) (reset! a -1))"]
+  ["get-validator"      "true"   "(let [a (atom 0)] (set-validator! a number?) (fn? (get-validator a)))"])
 
 (defspec "state / volatiles & delays"
   ["volatile! deref"    "0"      "(let [v (volatile! 0)] @v)"]