stdlib: port clojure.data, rewrite clojure.zip; fix with-meta nil; add battery

clojure.data: ported from the ClojureScript impl (jolt-native equality-partition
fn instead of host-type protocol dispatch). Verified against Clojure's own
data-test (12/13 canonical; the 13th needs nil-valued-map support, jolt-c7h).
Used mapv over the reference's (doall (map …)) — jolt's lazy multi-coll map +
doall don't force as a reduce accumulator (jolt-dzh).

clojure.zip: jolt's was a broken custom reimplementation; replaced with a port of
real clojure.zip (metadata-based locs). Uses (nth loc …) instead of (loc …)
because meta-bearing vectors aren't invocable as fns (jolt-vh5).

core: with-meta now accepts nil metadata (Clojure allows (with-meta x nil)); it
crashed calling keys on nil. This is what unblocked zip's make-node.

New vendored battery (test/clojure-stdlib/, from clojurust's suite with fixtures
corrected to match real Clojure): walk 34, zip 33, data 61 all clean; edn guarded
at 43 (still a stub — jolt-b7y). Conformance 218/218 all modes; full suite green.

test/clojure-stdlib/clojure/edn_test/read_string.cljc

@@ -0,0 +1,107 @@
+(ns clojure.edn-test.read-string
+  (:require [clojure.edn :as edn]
+            [clojure.test :refer [are deftest is testing]]))
+
+(deftest test-read-string-scalars
+  (testing "nil, booleans"
+    (is (nil? (edn/read-string "nil")))
+    (is (true? (edn/read-string "true")))
+    (is (false? (edn/read-string "false"))))
+
+  (testing "integers"
+    (is (= 0 (edn/read-string "0")))
+    (is (= 42 (edn/read-string "42")))
+    (is (= -1 (edn/read-string "-1")))
+    (is (= 1000000000000 (edn/read-string "1000000000000"))))
+
+  (testing "floats"
+    (is (= 3.14 (edn/read-string "3.14")))
+    (is (= -0.5 (edn/read-string "-0.5")))
+    (is (= 1.0 (edn/read-string "1.0"))))
+
+  (testing "bigints"
+    (is (= 42N (edn/read-string "42N"))))
+
+  (testing "bigdecimals"
+    (is (= 3.14M (edn/read-string "3.14M"))))
+
+  (testing "strings"
+    (is (= "" (edn/read-string "\"\"")))
+    (is (= "hello" (edn/read-string "\"hello\"")))
+    (is (= "line1\nline2" (edn/read-string "\"line1\\nline2\"")))
+    (is (= "tab\there" (edn/read-string "\"tab\\there\""))))
+
+  (testing "characters"
+    (is (= \a (edn/read-string "\\a")))
+    (is (= \newline (edn/read-string "\\newline")))
+    (is (= \space (edn/read-string "\\space")))
+    (is (= \tab (edn/read-string "\\tab"))))
+
+  (testing "keywords"
+    (is (= :foo (edn/read-string ":foo")))
+    (is (= :bar/baz (edn/read-string ":bar/baz"))))
+
+  (testing "symbols"
+    (is (= 'foo (edn/read-string "foo")))
+    (is (= 'bar/baz (edn/read-string "bar/baz")))))
+
+(deftest test-read-string-collections
+  (testing "vectors"
+    (is (= [] (edn/read-string "[]")))
+    (is (= [1 2 3] (edn/read-string "[1 2 3]")))
+    (is (= [1 [2 3] 4] (edn/read-string "[1 [2 3] 4]"))))
+
+  (testing "lists"
+    (is (= '() (edn/read-string "()")))
+    (is (= '(1 2 3) (edn/read-string "(1 2 3)")))
+    (is (= '(+ 1 2) (edn/read-string "(+ 1 2)"))))
+
+  (testing "maps"
+    (is (= {} (edn/read-string "{}")))
+    (is (= {:a 1} (edn/read-string "{:a 1}")))
+    (is (= {:a 1 :b 2} (edn/read-string "{:a 1 :b 2}")))
+    (is (= {:nested {:deep true}} (edn/read-string "{:nested {:deep true}}"))))
+
+  (testing "sets"
+    (is (= #{} (edn/read-string "#{}")))
+    (is (= #{1 2 3} (edn/read-string "#{1 2 3}"))))
+
+  (testing "mixed nested"
+    (is (= {:users [{:name "Alice" :age 30}
+                     {:name "Bob" :age 25}]}
+           (edn/read-string "{:users [{:name \"Alice\" :age 30} {:name \"Bob\" :age 25}]}")))))
+
+(deftest test-read-string-tagged-literals
+  (testing "#uuid"
+    (let [u (edn/read-string "#uuid \"f81d4fae-7dec-11d0-a765-00a0c91e6bf6\"")]
+      (is (uuid? u))
+      (is (= u (edn/read-string "#uuid \"f81d4fae-7dec-11d0-a765-00a0c91e6bf6\""))))))
+
+(deftest test-read-string-eof
+  (testing "empty string with :eof option"
+    (is (= :eof (edn/read-string {:eof :eof} "")))
+    (is (= nil (edn/read-string {:eof nil} "")))
+    (is (= 42 (edn/read-string {:eof 42} ""))))
+
+  (testing "whitespace-only with :eof option"
+    (is (= :done (edn/read-string {:eof :done} "   "))))
+
+  (testing "nil input returns nil"
+    (is (nil? (edn/read-string nil)))))
+
+(deftest test-read-string-comments
+  (testing "comments are skipped"
+    (is (= 42 (edn/read-string "; this is a comment\n42"))))
+
+  (testing "discard reader macro"
+    (is (= 2 (edn/read-string "#_ 1 2")))))
+
+(deftest test-read-string-only-first-form
+  (testing "reads only the first form"
+    (is (= 1 (edn/read-string "1 2 3")))
+    (is (= :a (edn/read-string ":a :b :c")))))
+
+(deftest test-read-string-ratios
+  (testing "ratios"
+    (is (= 1/2 (edn/read-string "1/2")))
+    (is (= 3/4 (edn/read-string "3/4")))))