Windows PowerShell started with detached: true exits 0 without running its command. Native Windows PowerShell launches (reveal and browser) now start attached, unref'd, with ignored stdio.

Takes over #10387. Fixes #11780.

Co-authored-by: doubletwisted <118005273+doubletwisted@users.noreply.github.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>