embed a namespace value spliced into a form (~*ns*)

A macro like (defmacro cur-ns [] `(str ~*ns*)) splices the live *ns* value
into its expansion, leaving an opaque jns object as a list element. The
analyzer had no way to carry a runtime value and threw uncompilable — the last
remaining corpus crash. Recognize a jns via the host contract (form-ns-value?)
and emit a :the-ns leaf that reconstructs it by name (intern-ns!) at the call
site, the same IR-leaf pattern as regex/inst/uuid. Closes unquote-*ns*-in-
template; corpus crash count -> 0.

A namespace fast path rather than a general constant pool: it's the only
embedded-value case in the corpus and the common real-world one (libs splice
~*ns*). A general pool can come later if other value types appear.

host/chez/host-contract.ss

@@ -62,6 +62,11 @@
 (define (hc-regex? x) (hc-tagged-of x hc-kw-regex))
 (define (hc-inst? x) (hc-tagged-of x hc-kw-inst))
 (define (hc-uuid? x) (hc-tagged-of x hc-kw-uuid))
+;; A live namespace value spliced into a form (e.g. `(str ~*ns*) in a macro):
+;; the analyzer can't carry an opaque runtime value, so recognize a jns and
+;; reconstruct it by name at the call site (jolt-8sha).
+(define (hc-ns-value? x) (jns? x))
+(define (hc-ns-value-name x) (jns-name x))
 
 ;; --- form accessors ---------------------------------------------------------
 (define (hc-char-code x) (char->integer x))  ; native Chez char -> codepoint
@@ -292,6 +297,8 @@
   (def-var! "jolt.host" "form-regex?" hc-regex?)
   (def-var! "jolt.host" "form-inst?" hc-inst?)
   (def-var! "jolt.host" "form-uuid?" hc-uuid?)
+  (def-var! "jolt.host" "form-ns-value?" hc-ns-value?)
+  (def-var! "jolt.host" "form-ns-value-name" hc-ns-value-name)
   (def-var! "jolt.host" "form-elements" hc-elements)
   (def-var! "jolt.host" "form-vec-items" hc-vec-items)
   (def-var! "jolt.host" "form-set-items" hc-set-items)

host/chez/run-corpus.ss

@@ -11,7 +11,7 @@
 ;; reset between cases so there is no leakage — same isolation a fresh process gives.
 ;;
 ;;   chez --script host/chez/run-corpus.ss
-;;   JOLT_CHEZ_ZJ_FLOOR=N   override the regression floor (default 2722)
+;;   JOLT_CHEZ_ZJ_FLOOR=N   override the regression floor (default 2723)
 ;;   JOLT_CORPUS_LIMIT=N    every-Nth stride (fast iteration; floor drops to 0)
 ;;   JOLT_DUMP_CRASH_LABELS=1   list crash + allowlisted labels
 (import (chezscheme))
@@ -192,7 +192,7 @@
 
 ;; Regression floor: fail on any NEW divergence or if pass drops below the floor.
 (define base-floor (let ((s (getenv "JOLT_CHEZ_ZJ_FLOOR")))
-                     (if s (string->number s) 2722)))
+                     (if s (string->number s) 2723)))
 (define floor (if limit 0 base-floor))
 (when (or (> (length diverged) 0) (< pass floor))
   (printf "REGRESSION: pass ~a < floor ~a or ~a new divergence(s)\n"