Chez Phase 3 inc 5d: add jolt.reader/read-all; reader port logic complete

read-all reads every top-level form of a string (the parse-all the compile path
needs in inc 6). With this the portable reader covers everything reader.janet does
(atoms 5a, collections+quote/meta 5b, dispatch 5c, multi-form 5d).

Validated: reader-parity 149/149 (every construct); jolt.reader compiles and runs
on build/jolt ((require [jolt.reader]) (read-all …) works natively). The
interpreted reader overflows the eval stack on large/deeply-nested files, so real-
file/full-corpus validation happens when it's cross-compiled and run on Chez
(inc 7). Position tracking (checker) and the actual wire-in replacing reader.ss are
deferred — they ride inc 6 (jolt.reader on Chez). See new beads.

jolt-core/jolt/reader.clj

@@ -455,3 +455,16 @@
   "Read the first form of `s` (skipping leading trivia). Returns the form."
   [s]
   (first (read-next-form s 0)))
+
+(defn read-all
+  "Read every top-level form of `s`, returning them in a vector (trivia skipped)."
+  [s]
+  (loop [pos 0 acc []]
+    (let [p (skip-whitespace s pos)]
+      (if (>= p (len s))
+        acc
+        (let [[kind payload np] (read-form s p)]
+          (case kind
+            :skip (recur np acc)
+            :splice (recur np (into acc payload))
+            :form (recur np (conj acc payload))))))))