reflective: extract env.sx + migrate Kernel — 322 tests green

Phase 1 of the lib-guest-reflective extraction plan.

lib/guest/reflective/env.sx — canonical wire shape
{:refl-tag :env :bindings DICT :parent ENV-OR-NIL} with mutable
defaults (dict-set!), plus *-with adapter-cfg variants for consumers
with their own shape (modelled after lib/guest/match.sx). 13 forms,
~5 KB.

lib/kernel/eval.sx — env block collapses from ~30 lines to 6 thin
wrappers (kernel-env? = refl-env?, etc.). No semantic change; envs
now carry :refl-tag :env instead of :knl-tag :env. All 322 Kernel
tests pass unchanged across 7 suites (parse 62, eval 36, vau 38,
standard 127, encap 19, hygiene 26, metacircular 14).

Next: Phase 2 — Tcl adapter cfg in lib/tcl/runtime.sx using
refl-env-lookup-with against the existing :level/:locals/:parent
frame shape.

lib/kernel/eval.sx

@@ -7,9 +7,11 @@
 ;;
 ;; Tagged values
 ;; -------------
-;;   {:knl-tag :env :bindings DICT :parent PARENT-OR-NIL}
+;;   {:refl-tag :env :bindings DICT :parent PARENT-OR-NIL}
 ;;     A first-class Kernel environment. Bindings is a mutable SX dict
-;;     keyed by symbol name; parent walks up the lookup chain.
+;;     keyed by symbol name; parent walks up the lookup chain. Shape
+;;     and operations are inherited from lib/guest/reflective/env.sx
+;;     (canonical wire shape) — Kernel-side names are thin wrappers.
 ;;
 ;;   {:knl-tag :operative :impl FN}
 ;;     Primitive operative. FN receives (args dyn-env) — args are the
@@ -42,38 +44,16 @@
 ;;
 ;; Consumes: lib/kernel/parser.sx (kernel-string?, kernel-string-value)
 
-;; ── Environments — first-class, pure-SX (binding dict + parent) ──
+;; ── Environments — delegated to lib/guest/reflective/env.sx ──────
+;; The env values themselves now carry `:refl-tag :env` (shared with the
+;; reflective kit). Kernel's API names stay; bodies are thin wrappers.
 
-(define kernel-env? (fn (v) (and (dict? v) (= (get v :knl-tag) :env))))
-
-(define kernel-make-env (fn () {:parent nil :knl-tag :env :bindings {}}))
-
-(define kernel-extend-env (fn (parent) {:parent parent :knl-tag :env :bindings {}}))
-
-(define
-  kernel-env-bind!
-  (fn (env name val) (dict-set! (get env :bindings) name val) val))
-
-(define
-  kernel-env-has?
-  (fn
-    (env name)
-    (cond
-      ((nil? env) false)
-      ((not (kernel-env? env)) false)
-      ((dict-has? (get env :bindings) name) true)
-      (:else (kernel-env-has? (get env :parent) name)))))
-
-(define
-  kernel-env-lookup
-  (fn
-    (env name)
-    (cond
-      ((nil? env) (error (str "kernel-eval: unbound symbol: " name)))
-      ((not (kernel-env? env))
-        (error (str "kernel-eval: corrupt env: " env)))
-      ((dict-has? (get env :bindings) name) (get (get env :bindings) name))
-      (:else (kernel-env-lookup (get env :parent) name)))))
+(define kernel-env?        refl-env?)
+(define kernel-make-env    refl-make-env)
+(define kernel-extend-env  refl-extend-env)
+(define kernel-env-bind!   refl-env-bind!)
+(define kernel-env-has?    refl-env-has?)
+(define kernel-env-lookup  refl-env-lookup)
 
 ;; ── Tagged-value constructors and predicates ─────────────────────