kb v0.5.0

What's Changed

• 306b9ad fix: split launcher test by OS (macOS uses 'open', not 'xdg-open')
• 3a78615 fix: import unix PermissionsExt in editor test shim
• 5459a70 chore: release v0.5.0
• 549de0d feat: v0.5.0 - kb open, kb archive, doctor --fix, day-1 hardening

Full Changelog: v0.4.0...v0.5.0