Finish Electron shell and workflow wiring

tests/checks/test_startup_smoke.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+# Workflow check: ensure the Electron launcher boots without the
+# ELECTRON_RUN_AS_NODE shim leaking into the app process.
+
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+cd "$ROOT_DIR"
+
+TMP_ROOT="$(mktemp -d)"
+trap 'rm -rf "$TMP_ROOT"' EXIT
+
+LOG_FILE="$TMP_ROOT/start.log"
+set +e
+STEPFORGE_DATA_DIR="$TMP_ROOT/data" timeout 8s npm start >"$LOG_FILE" 2>&1
+status=$?
+set -e
+
+if [[ $status -ne 124 ]]; then
+  cat "$LOG_FILE" >&2
+  echo "electron launcher did not stay alive under timeout (status $status)" >&2
+  exit 1
+fi
+
+if grep -Eq 'TypeError: Cannot read properties of undefined \(reading '\''requestSingleInstanceLock'\''\)|bad option: --ozone-platform=headless' "$LOG_FILE"; then
+  cat "$LOG_FILE" >&2
+  echo "launcher still exposed a Node-mode startup failure" >&2
+  exit 1
+fi
+
+echo "startup smoke OK"