Move stdlib out of spec — clean spec/library boundary

spec/ now contains only the language definition (5 files):
  evaluator.sx, parser.sx, primitives.sx, render.sx, special-forms.sx

lib/ contains code written IN the language (8 files):
  stdlib.sx, types.sx, freeze.sx, content.sx,
  bytecode.sx, compiler.sx, vm.sx, callcc.sx

Test files follow source: spec/tests/ for core language tests,
lib/tests/ for library tests (continuations, freeze, types, vm).

Updated all consumers:
- JS/Python/OCaml bootstrappers: added lib/ to source search paths
- OCaml bridge: spec_dir for parser/render, lib_dir for compiler/freeze
- JS test runner: scans spec/tests/ (always) + lib/tests/ (--full)
- OCaml test runner: scans spec/tests/, lib tests via explicit request
- Docker dev mounts: added ./lib:/app/lib:ro

Tests: 1041 JS standard, 1322 JS full, 1101 OCaml — all pass

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

lib/content.sx

@@ -0,0 +1,48 @@
+;; ==========================================================================
+;; content.sx — 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.
+;;
+;; This is a library built on top of freeze.sx. It is NOT part of the
+;; core evaluator. Load order: evaluator.sx → freeze.sx → content.sx
+;;
+;; 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))))