feat: add bundle-host-test.cjs + smoke integration

- bundle-host-test.cjs: JS smoke-test for PluginBundleHost contract
  - 4 error boundary scenarios (missing frontend, JS throw, missing component, mount throw)
  - 5 real mount scenarios (bundle exec, DiagnosticsPanel mount, Settings mount, unmount, mount-throw catch)
  - Runs real platform-test bundle in vm.Sandbox with mock window/document
- smoke-platform.sh: add bundle-host-test step
- Fix: platform-test badgeRow div call (3rd arg was ignored)

scripts/smoke-platform.sh

@@ -73,9 +73,6 @@ if [ "$SMOKE_ED_EXIT" -ne 0 ]; then
   exit 1
 fi
 
-echo ""
-echo "✅ smoke-platform done"
-
 # ── test workspace via Go smoke ──
 echo ""
 echo "[go smoke: workspace]"
@@ -96,5 +93,19 @@ if [ "$SMOKE_CONT_EXIT" -ne 0 ]; then
   exit 1
 fi
 
+# ── bundle host test (JS smoke for error boundary + real mount proof) ──
+echo ""
+echo "[bundle host test]"
+if ! command -v node &>/dev/null; then
+  echo "  ⚠️  node not found — skipping bundle-host-test"
+else
+  (node "$ROOT/frontend/tests/bundle-host-test.cjs" 2>&1)
+  BUNDLE_HOST_EXIT=$?
+  if [ "$BUNDLE_HOST_EXIT" -ne 0 ]; then
+    echo "  ❌ bundle-host-test failed"
+    exit 1
+  fi
+fi
+
 echo ""
 echo "✅ smoke-platform all tests done"