tests: pin ink engine in _make_tui_argv npm-bootstrap tests (post-merge semantic fix)

Main's rewritten test_tui_npm_install.py tests call _make_tui_argv expecting
the Ink/npm flow unconditionally; with the dual-engine dispatch merged in,
_resolve_tui_engine() auto-selects opentui whenever ui-opentui/dist is built
in the repo, routing the call away from the path under test (first subprocess
became 'node --version' instead of 'npm run build'). Pin the engine to ink
via an autouse fixture, mirroring the existing pinning precedent in
test_tui_resume_flow.py.

apps/desktop/electron/bootstrap-runner.cjs

@@ -40,6 +40,15 @@ const path = require('node:path')
 const https = require('node:https')
 const { spawn } = require('node:child_process')
 
+const IS_WINDOWS = process.platform === 'win32'
+
+function hiddenWindowsChildOptions(options = {}) {
+  if (!IS_WINDOWS || Object.prototype.hasOwnProperty.call(options, 'windowsHide')) {
+    return options
+  }
+  return { ...options, windowsHide: true }
+}
+
 const STAMP_COMMIT_RE = /^[0-9a-f]{7,40}$/i
 
 // Stages flagged needs_user_input=true in the manifest are skipped by the
@@ -284,7 +293,7 @@ function spawnPowerShell(scriptPath, args, { emit, stageName, abortSignal, herme
     const ps = process.platform === 'win32' ? resolveWindowsPowerShell() : 'pwsh'
     const fullArgs = ['-NoProfile', '-ExecutionPolicy', 'Bypass', '-File', scriptPath, ...args]
 
-    const child = spawn(ps, fullArgs, {
+    const child = spawn(ps, fullArgs, hiddenWindowsChildOptions({
       stdio: ['ignore', 'pipe', 'pipe'],
       env: {
         ...process.env,
@@ -292,7 +301,7 @@ function spawnPowerShell(scriptPath, args, { emit, stageName, abortSignal, herme
         // choice rather than re-computing the default.
         HERMES_HOME: hermesHome || process.env.HERMES_HOME || ''
       }
-    })
+    }))
 
     let stdout = ''
     let stderr = ''