More library-compat fixes from porting the examples (markdown, malli)

Reader / loader:
- #?@ splicing reader conditionals now actually splice the matched collection's
  items into the enclosing sequence; the splice flag was read but ignored, so a
  binding vector like [a #?@(:clj [b (.foo b)])] lost its alignment.
- the file loader reads by position and skips a top-level form that reads as
  nothing (a :cljs-only #?, a #_ discard, a trailing comment) instead of
  treating it as EOF — which silently dropped the rest of a large .cljc file.
- jolt's reader feature set now includes :clj (was {:jolt :default}). jolt is a
  Clojure/JVM-compatible host that emulates clojure.lang.* and java.* interop,
  so it reads the :clj branch of a .cljc library, not :cljs. This also lets four
  more reader-conditional corpus cases pass (floor 2726 -> 2730).

Backend:
- munge-name escapes ' (prime) -> _PRIME_; a Clojure symbol like f' otherwise
  emitted a bare ' into Scheme, which is the quote reader macro and unbalanced
  the output.

Host shims:
- clojure.java.io/writer (pass through a StringWriter, file-back a path) and a
  readLine on the string reader, so line-seq over (io/reader …) works (markdown).

A better "unsupported destructuring pattern: <pat>" error message.

jolt-core/clojure/core/00-syntax.clj

@@ -247,7 +247,7 @@
                                a
                                (proc k `(get ~gm ~(get pat k)) a)))
                            g3 (keys pat)))
-               :else (throw (str "unsupported destructuring pattern"))))
+               :else (throw (str "unsupported destructuring pattern: " (pr-str pat)))))
          ploop
            (fn* ploop [i acc]
              (if (< i (count bindings))

jolt-core/jolt/backend_scheme.clj

@@ -120,7 +120,13 @@
 ;; starts a datum in Scheme, so replace it with `_`. A name that collides with a
 ;; Scheme keyword is prefixed with `_` so it can never shadow the emitted form.
 (defn- munge-name [s]
-  (let [s (str/replace s "#" "_")]
+  ;; A Clojure symbol may contain chars that break a Scheme identifier: ' is the
+  ;; quote reader macro (a bare f' would read as f then 'rest), # already maps to
+  ;; _. Munge both to safe tokens; the same mapping applies at the binding and at
+  ;; every reference, so resolution stays consistent.
+  (let [s (-> s
+              (str/replace "#" "_")
+              (str/replace "'" "_PRIME_"))]
     (if (contains? scheme-reserved s) (str "_" s) s)))
 
 (declare emit)