Fix blank terminal on macOS 26 and macOS 15:
- Add macOS 26 guard to two additional code paths that set window non-opaque
- Fix NSVisualEffectView z-order: add to themeFrame instead of contentView
- Align sidebarBlendMode defaults between @AppStorage and UserDefaults
- Add read_screen socket command and blank screen regression test
- Add reloads.sh staging script
