VM import suspension for browser lazy loading

Bytecode compiler now emits OP_PERFORM for (import ...) and compiles
(define-library ...) bodies. The VM stores the import request in
globals["__io_request"] and stops the run loop — no exceptions needed.
vm-execute-module returns a suspension dict, vm-resume-module continues.

Browser: sx_browser.ml detects suspension dicts from execute_module and
returns JS {suspended, op, request, resume} objects. The sx-platform.js
while loop handles cascading suspensions via handleImportSuspension.

13 modules load via .sxbc bytecode in 226ms (manifest-driven), both
islands hydrate, all handlers wired. 2650/2650 tests pass including
6 new vm-import-suspension tests.

Also: consolidated sx-platform-2.js → sx-platform.js, fixed
vm-execute-module missing code-from-value call, fixed bootstrap.py
protocol registry transpiler issues.

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

hosts/ocaml/browser/test_wasm.sh

@@ -95,7 +95,7 @@ node -e '
   var K = globalThis.SxKernel;
   if (!K) { console.error("FAIL: SxKernel not found"); process.exit(1); }
 
-  // --- Register 8 FFI host primitives (normally done by sx-platform-2.js) ---
+  // --- Register 8 FFI host primitives (normally done by sx-platform.js) ---
   K.registerNative("host-global", function(args) {
     var name = args[0];
     if (typeof globalThis !== "undefined" && name in globalThis) return globalThis[name];
@@ -195,7 +195,7 @@ node -e '
   assert("is-html-tag? fake", K.eval("(is-html-tag? \"fake\")"), false);
 
   // =====================================================================
-  // Load web stack modules (same as sx-platform-2.js loadWebStack)
+  // Load web stack modules (same as sx-platform.js loadWebStack)
   // =====================================================================
   var fs = require("fs");
   var webStackFiles = [