fix(macos): hide duplicate bitsdojo window buttons in title bar

[ZhuchkaTriplesix]

Parent

Part of epic #490. Related to #473 custom frame.

Problem

QueryaWindowTitleBar reserves leading inset for macOS traffic lights, but always renders MinimizeWindowButton / MaximizeWindowButton / CloseWindowButton on the right → likely duplicate window controls on macOS.

Proposal

Hide bitsdojo window buttons when Platform.isMacOS; keep leading inset. Keep buttons on Windows/Linux.

Files

• lib/features/main_screen/querya_window_title_bar.dart

Acceptance

• macOS: only system traffic lights (no second button strip)
• Windows/Linux: Minimize/Maximize/Close still present
• Title-bar goldens / layout tests updated if needed

[ZhuchkaTriplesix]

Shipped on dev via #513.