Content-addressed computation: freeze → hash → CID → thaw

Hash frozen SX to a content identifier (djb2 → hex). Same state
always produces the same CID. Store by CID, retrieve by CID.

- content-hash: djb2 hash of SX text → hex string
- content-put/get: in-memory content store
- freeze-to-cid: freeze scope → store → return CID
- thaw-from-cid: look up CID → thaw signals
- char-code-at / to-hex primitives for both platforms
- Live demo: counter + name widget, content-address button,
  CID display, restore from CID input, CID history

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

shared/sx/ref/cek.sx

@@ -1129,3 +1129,50 @@
           (cek-thaw-scope (get frozen "name") frozen))))))
 
 
+
+
+;; --------------------------------------------------------------------------
+;; 14. Content-addressed computation
+;; --------------------------------------------------------------------------
+;;
+;; Hash frozen SX to a content identifier. Store and retrieve by CID.
+;; The content IS the address — same SX always produces the same CID.
+;;
+;; Uses an in-memory content store. Applications can persist to
+;; localStorage or IPFS by providing their own store backend.
+
+(define content-store (dict))
+
+(define content-hash :effects []
+  (fn (sx-text)
+    ;; djb2 hash → hex string. Simple, deterministic, fast.
+    ;; Real deployment would use SHA-256 / multihash.
+    (let ((hash 5381))
+      (for-each (fn (i)
+        (set! hash (mod (+ (* hash 33) (char-code-at sx-text i)) 4294967296)))
+        (range 0 (len sx-text)))
+      (to-hex hash))))
+
+(define content-put :effects [mutation]
+  (fn (sx-text)
+    (let ((cid (content-hash sx-text)))
+      (dict-set! content-store cid sx-text)
+      cid)))
+
+(define content-get :effects []
+  (fn (cid)
+    (get content-store cid)))
+
+;; Freeze a scope → store → return CID
+(define freeze-to-cid :effects [mutation]
+  (fn (scope-name)
+    (let ((sx-text (freeze-to-sx scope-name)))
+      (content-put sx-text))))
+
+;; Thaw from CID → look up → restore
+(define thaw-from-cid :effects [mutation]
+  (fn (cid)
+    (let ((sx-text (content-get cid)))
+      (when sx-text
+        (thaw-from-sx sx-text)
+        true))))