fix: restore plan canvas process launcher

scripts/control-pane.js

@@ -1,8 +1,6 @@
 #!/usr/bin/env node
 'use strict';
 
-const { spawn } = require('child_process');
-
 const {
   createControlPaneServer,
   parseArgs,

scripts/plan-canvas.js

@@ -20,6 +20,7 @@
 const fs = require('fs');
 const http = require('http');
 const path = require('path');
+const { spawn } = require('child_process');
 const {
   canonicalizeArtifactPath,
   createSessionStore,

tests/scripts/control-pane.test.js

@@ -602,11 +602,11 @@ async function runTests() {
   else failed++;
 
   if (
-    await test('CLI browser opener handles spawn errors', async () => {
+    await test('CLI browser opener delegates spawn errors to the shared launcher', async () => {
       const source = fs.readFileSync(SCRIPT, 'utf8');
 
-      assert.match(source, /child\.on\('error'/);
-      assert.match(source, /child\.unref\(\)/);
+      assert.match(source, /openBrowser: launchOpenBrowser/);
+      assert.match(source, /launchOpenBrowser\(url\)/);
     })
   )
     passed++;