[Bug]: Enabling Upkeep from Powershell 7 does not work

### TWG CLI version

1.2.5

### Operating system

Windows 11

### Command or agent request

twg upkeep enable

### Expected behavior

TWG upkeep enabled every 12 minutes via windows-task-scheduler.
Launcher: C:\Users\...\AppData\Local\Programs\twg\bin\twg.exe
OAuth refresh runs only near expiry. Update checks notify you but never install automatically.
Initial maintenance: OAuth fresh; update check current.
The per-user scheduler can maintain the persistent OAuth session stored in your TWG config directory.

### Actual behavior

Error: PowerShell scheduler command failed: PowerShell reported no detail.
Code: TWG_COMMAND_FAILED

Start by reproducing `twg upkeep enable` with TWG CLI 1.2.5 in PowerShell 7 on Windows 11, focusing on the Windows Task Scheduler command and the reported lack of PowerShell detail. Done means the command succeeds and enables the per-user scheduler with the expected 12-minute upkeep behavior.

Written by the indexing model from the issue text.