Load freeze.sx + browser API stubs for complete island SSR

All islands now render server-side:
- freeze.sx loaded into kernel (freeze-scope for home/stepper)
- Browser-only APIs stubbed (local-storage-get/set, dom-listen,
  dom-dispatch, dom-set-data, dom-get-data, promise-then)
  → return nil on server, client hydrates with real behavior

Zero island failures. Both layouts/header and home/stepper render
with hydration markers, CSS classes, and initial signal values.

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

shared/sx/ocaml_bridge.py

@@ -397,14 +397,18 @@ class OcamlBridge:
             # All directories loaded into the Python env
             all_dirs = list(set(_watched_dirs) | _dirs_from_cache)
 
-            # Web adapters + signals (aser lives in adapter-sx.sx,
-            # signals.sx provides reactive primitives for island SSR)
+            # Isomorphic libraries: signals, rendering, freeze scopes
             web_dir = os.path.join(os.path.dirname(__file__), "../../web")
             if os.path.isdir(web_dir):
                 for web_file in ["signals.sx", "adapter-html.sx", "adapter-sx.sx"]:
                     path = os.path.normpath(os.path.join(web_dir, web_file))
                     if os.path.isfile(path):
                         all_files.append(path)
+            # Spec library files (loaded after adapters)
+            for spec_lib in ["freeze.sx"]:
+                path = os.path.normpath(os.path.join(spec_dir, spec_lib))
+                if os.path.isfile(path):
+                    all_files.append(path)
 
             for directory in sorted(all_dirs):
                 files = sorted(