Step 15: bytecode + CEK state serialization — 16 tests

bytecode-serialize/deserialize: sxbc v2 format wrapping compiled code
dicts. cek-serialize/deserialize: cek-state v1 format wrapping suspended
CEK state (phase, request, env, kont). Both use SX s-expression
round-trip via inspect/parse. lib/serialize.sx has pure SX versions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/serialize.sx

@@ -0,0 +1,39 @@
+;; Bytecode + CEK state serialization
+;; Uses SX s-expression format for portability across all hosts.
+
+;; ── Bytecode serialization ────────────────────────────────────────
+
+(define
+  bytecode-serialize
+  (fn (code) (str "(sxbc 2 " (serialize code) ")")))
+
+(define
+  bytecode-deserialize
+  (fn
+    (s)
+    (let
+      ((parsed (first (sx-parse s))))
+      (if
+        (and (list? parsed) (>= (len parsed) 3) (= (first parsed) "sxbc"))
+        (nth parsed 2)
+        (error "bytecode-deserialize: invalid sxbc format")))))
+
+;; ── CEK state serialization ───────────────────────────────────────
+
+(define
+  cek-serialize
+  (fn (state) (str "(cek-state 1 " (serialize state) ")")))
+
+(define
+  cek-deserialize
+  (fn
+    (s)
+    (let
+      ((parsed (first (sx-parse s))))
+      (if
+        (and
+          (list? parsed)
+          (>= (len parsed) 3)
+          (= (first parsed) "cek-state"))
+        (nth parsed 2)
+        (error "cek-deserialize: invalid cek-state format")))))