fix(dev): clean up web backend lifecycle

scripts/dev-server-command.test.mjs

@@ -1,7 +1,7 @@
 import assert from 'node:assert/strict'
 import test from 'node:test'
 
-import { createChatlabStartCommand } from './dev-server-command.mjs'
+import { createChatlabStartCommand, terminateChatlabStartProcess } from './dev-server-command.mjs'
 
 test('web dev backend runs through the current Node executable with the tsx loader', () => {
   const command = createChatlabStartCommand({
@@ -25,4 +25,28 @@ test('web dev backend runs through the current Node executable with the tsx load
     '--port',
     '3110',
   ])
+  assert.equal(command.options.detached, true)
+})
+
+test('web dev backend cleanup terminates the whole POSIX process group', () => {
+  const killed = []
+  const proc = {
+    pid: 12345,
+    exitCode: null,
+    signalCode: null,
+    kill(signal) {
+      killed.push(['child', signal])
+      return true
+    },
+  }
+
+  terminateChatlabStartProcess(proc, {
+    platform: 'darwin',
+    killProcess: (pid, signal) => {
+      killed.push(['process', pid, signal])
+      return true
+    },
+  })
+
+  assert.deepEqual(killed, [['process', -12345, 'SIGTERM']])
 })