Remove cssx.sx references from WASM test scripts

cssx.sx was deleted in the CSSX → ~tw migration. The test scripts
(test_wasm.sh, test_wasm_native.js, bisect_sxbc.sh) still referenced
it, causing ENOENT during WASM build step 5.

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

hosts/ocaml/browser/test_wasm_native.js

@@ -125,7 +125,7 @@ async function main() {
     'render', 'core-signals', 'signals', 'deps', 'router', 'page-helpers', 'freeze',
     'bytecode', 'compiler', 'vm', 'dom', 'browser',
     'adapter-html', 'adapter-sx', 'adapter-dom',
-    'cssx', 'boot-helpers', 'hypersx',
+    'boot-helpers', 'hypersx',
     'harness', 'harness-reactive', 'harness-web',
     'engine', 'orchestration', 'boot',
   ];