Compile data readers that return code forms

A registered #tag data reader whose fn returns a FORM (borkdude/html's #html
expands to (->Html (str …))) was rewritten to a runtime call (reader-fn 'inner),
so the returned code became a runtime list value instead of being compiled —
(str #html [:div]) rendered the code, not "<div>". Clojure applies a data reader
at read time and substitutes its result as code.

loader.ss now applies the reader at load time: a code form (a list) is spliced in
to be compiled, a value (time-literals #time/date -> a Date) keeps the runtime
call, which also keeps a non-serializable constant out of an AOT build. The build
emit path never applied data readers at all (a #tag literal failed a `jolt build`
with "unsupported form"); emit-image.ss gets an ei-emit-form-hook the build sets
to the same rewrite, left as a no-op elsewhere so the seed mint (which doesn't
load loader.ss) is unaffected and the self-host byte-fixpoint holds.

Also make clojure.test report the actual values of a failing (is (= a b)) — it
printed only the form. Restricted to the common pure predicates so a macro head
still takes the plain path.

Fixture test/chez/datareader-app + a smoke check (interpreted) and a build-smoke
check (AOT). make test green, no corpus change.

host/chez/build.ss

@@ -449,6 +449,11 @@
                 ;; whole-program param-type fixpoint before per-form emit
                 (when (string=? mode "optimized") (bld-wp-infer! ordered)))
               (lambda ()
+                ;; A #tag data-reader literal must compile in the binary the same as
+                ;; it loads interpreted — apply the reader rewrite to each emitted
+                ;; form too (no-op unless the app registered data readers).
+                (parameterize ((ei-emit-form-hook
+                                (lambda (form) (if data-readers-active (ldr-apply-readers form) form))))
                 (if tree-shake?
                     (dce-shake
                       (dce-blob-records "host/chez/seed/prelude.ss")
@@ -473,7 +478,7 @@
                                          (append (bld-ns-prelude (car nf) src)
                                                  (bld-emit-ns (car nf) src)))))
                                    ordered))
-                            #f)))
+                            #f))))
               (lambda ()
                 (set-optimize! #f)
                 ((var-deref "jolt.backend-scheme" "set-direct-link!") #f)))))