fix(dev): stop stale frontend when portal exits

scripts/dev-process-lifecycle.test.mjs

@@ -0,0 +1,47 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { handleUnexpectedChildExit } from './dev-process-lifecycle.mjs';
+
+function invokeExit({ code, signal, stopping = false }) {
+  const shutdownCodes = [];
+  const messages = [];
+  const handled = handleUnexpectedChildExit({
+    label: 'portal',
+    code,
+    signal,
+    stopping,
+    shutdown: (shutdownCode) => shutdownCodes.push(shutdownCode),
+    log: (message) => messages.push(message),
+  });
+  return { handled, shutdownCodes, messages };
+}
+
+test('clean child exit shuts down the remaining dev stack as a failure', () => {
+  const result = invokeExit({ code: 0, signal: null });
+
+  assert.equal(result.handled, true);
+  assert.deepEqual(result.shutdownCodes, [1]);
+  assert.match(result.messages[0], /code 0/);
+});
+
+test('signal exit shuts down the remaining dev stack as a failure', () => {
+  const result = invokeExit({ code: null, signal: 'SIGKILL' });
+
+  assert.equal(result.handled, true);
+  assert.deepEqual(result.shutdownCodes, [1]);
+  assert.match(result.messages[0], /signal SIGKILL/);
+});
+
+test('non-zero child exit preserves its failure code', () => {
+  const result = invokeExit({ code: 7, signal: null });
+
+  assert.deepEqual(result.shutdownCodes, [7]);
+});
+
+test('child exits during an intentional shutdown are ignored', () => {
+  const result = invokeExit({ code: 0, signal: null, stopping: true });
+
+  assert.equal(result.handled, false);
+  assert.deepEqual(result.shutdownCodes, []);
+  assert.deepEqual(result.messages, []);
+});