Move the Chez test oracle off Janet

The unit tests in test/chez/_*.janet now drive bin/joltc (the zero-Janet
spine) and judge against baked expected values instead of a live build/jolt
run. Ten of them captured the oracle from build/jolt per case; their values
are now literals (one env-dependent javastatic case became a predicate so it
stays portable). The rest already had literal expecteds with a redundant
build/jolt sanity check, now dropped.

Retire emit-test/emit-parity/reader-parity: they compared the Chez/Clojure
path against a live Janet evaluation, emitter, or reader. That migration check
is done, and run-corpus-zero-janet (Chez analyzer vs the JVM corpus) plus
certify.clj cover correctness now.

Rewrite the README for the current zero-Janet gate.

jolt-5oci

test/chez/_str.janet

@@ -1,11 +1,11 @@
 # jolt-nfca — host java.lang.String method interop on Chez: (.toUpperCase s),
 # (.indexOf s x), (.substring s a b), the regex methods (.matches/.replaceAll/
-# .replaceFirst), etc. Ported from the seed's string-methods surface
-# (src/jolt/eval_resolve.janet). Expectations are the build/jolt (seed) oracle.
+# .replaceFirst), etc. The string-methods surface. Each case carries its
+# expected value.
 # An expected of :throws asserts a non-zero exit (unsupported method).
 #
 #   janet test/chez/_str.janet
-(def jolt-bin (or (os/getenv "JOLT_BIN") "bin/jolt-chez"))
+(def jolt-bin (or (os/getenv "JOLT_BIN") "bin/joltc"))
 
 (def cases
   [["toLowerCase"      "(.toLowerCase \"HI\")"                  "hi"]