Chez Phase 2 (inc X): #inst / #uuid literals + java.time (jolt-at0a)

The analyzer lowers a #inst/#uuid tagged form to a :inst/:uuid IR leaf, mirroring
the existing :regex node: the Janet back end punts to the interpreter (its
data-readers parse the literal, so seed behavior is unchanged), the Chez back end
emits jolt-inst-from-string / jolt-uuid-from-string.

host/chez/inst-time.ss is the Chez-native value layer: a jinst record holding
epoch ms (RFC3339 parsed via Hinnant civil/days math, with Clojure's partial
defaults and +/-hh:mm offsets), wired into jolt-get (so the overlay inst?/inst-ms
read it), jolt= / jolt-hash (instant identity as a map key), pr-str (#inst
"...-00:00"), str, type, and instance? java.util.Date. The java.time surface
(DateTimeFormatter ofPattern/ISO_LOCAL_DATE_TIME/ofLocalized*, the pattern engine,
Instant, ZoneId, LocalDateTime, FormatStyle, Locale, Date) ports java_base.janet
over host-static.ss's registries.

Corpus 2202->2238, 0 new divergences; clears the whole 'unsupported form'
emit-fail bucket. Full Janet gate green (analyzer/backend changes are
behaviour-preserving — #inst still parses through the interpreter's data-readers
on the seed).

host/chez/natives-misc.ss

@@ -26,6 +26,10 @@
             (loop (fx+ i 1)))))))
 (define (jolt-random-uuid) (make-juuid (random-uuid-str)))
 
+;; #uuid literal -> a uuid value (emit.janet lowers the :uuid node to this). The
+;; reader already validated the shape; lowercase for value equality.
+(define (jolt-uuid-from-string s) (make-juuid (string-downcase s)))
+
 ;; parse-uuid: validate the canonical shape (8-4-4-4-12 hex), lowercase, -> uuid;
 ;; nil if the string doesn't conform (Clojure parse-uuid), error on a non-string.
 (define (hex-char? c) (or (and (char>=? c #\0) (char<=? c #\9))