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/emit.janet

@@ -503,6 +503,10 @@
     # in the pattern becomes \\ in the Scheme string literal -> the 1-char
     # backslash irregex expects (same escaping emit-const uses for strings).
     :regex (string "(jolt-regex " (chez-str-lit (get node :source)) ")")
+    # #inst / #uuid literals -> a runtime inst / uuid value (inst-time.ss /
+    # natives-misc.ss). The source string round-trips through chez-str-lit.
+    :inst (string "(jolt-inst-from-string " (chez-str-lit (get node :source)) ")")
+    :uuid (string "(jolt-uuid-from-string " (chez-str-lit (get node :source)) ")")
     # host interop (jolt-0kf5): (.method target arg*) -> (jolt-host-call "method"
     # target arg*). Only the methods the RT dispatcher (rt.ss) actually shims are
     # IN the subset; any other method is out of subset (a clean emit-time reject,