Transparent lazy module loading — code loads like data

When the VM or CEK hits an undefined symbol, it checks a symbol→library
index (built from manifest exports at boot), loads the library that
exports it, and returns the value. Execution continues as if the module
was always loaded. No import statements, no load-library! calls, no
Suspense boundaries — just call the function.

This is the same mechanism as IO suspension for data fetching. The
programmer doesn't distinguish between calling a local function and
calling one that needs its module fetched first. The runtime treats
code as just another resource.

Implementation:
- _symbol_resolve_hook in sx_types.ml — called by env_get_id (CEK path)
  and vm_global_get (VM path) when a symbol isn't found
- Symbol→library index built from manifest exports in sx-platform.js
- __resolve-symbol native calls __sxLoadLibrary, module loads, symbol
  appears in globals, execution resumes
- compile-modules.js extracts export lists into module-manifest.json
- Playground page demonstrates: (freeze-scope) triggers freeze.sxbc
  download transparently on first use

2650/2650 tests pass.

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

hosts/ocaml/browser/compile-modules.js

@@ -279,6 +279,20 @@ function extractImportDeps(source) {
   return deps;
 }
 
+// Extract exported symbol names from (export name1 name2 ...) clause
+function extractExports(source) {
+  const exports = [];
+  const m = source.match(/\(export\s+([\s\S]*?)\)\s*\(/);
+  if (!m) return exports;
+  // Parse symbol names from the export list (skip keywords, nested forms)
+  const tokens = m[1].split(/\s+/).filter(t => t && !t.startsWith(':') && !t.startsWith('(') && !t.startsWith(')'));
+  for (const t of tokens) {
+    const clean = t.replace(/[()]/g, '');
+    if (clean && !clean.startsWith(':')) exports.push(clean);
+  }
+  return exports;
+}
+
 // Flatten library spec: "(sx dom)" → "sx dom"
 function libKey(spec) {
   return spec.replace(/^\(/, '').replace(/\)$/, '');
@@ -296,9 +310,11 @@ for (const file of FILES) {
   const sxbcFile = file.replace(/\.sx$/, '.sxbc');
 
   if (libName) {
+    const exports = extractExports(src);
     manifest[libKey(libName)] = {
       file: sxbcFile,
       deps: deps.map(libKey),
+      exports: exports,
     };
   } else if (deps.length > 0) {
     // Entry point (no define-library, has imports)