Allow switching window controls (custom ↔ macOS) and position

[remcostoeten]

Summary

Let users switch the window control style between the current custom controls and macOS-style controls, and optionally configure their position (e.g. left/right).

Notes

• Persist the choice in settings.
• Make sure panels (e.g. the AI panel — see Decrease AI panel height so it sits below top window controls #164) lay out correctly under whichever control style/position is chosen.

[remcostoeten]

PR #222 ships the style half: Settings → Interface → Window Controls now switches between the custom buttons and macOS-style traffic lights, persisted in settings.

Still open: the position (left/right) half. WindowControls is mounted in ~7 different header rightSlots (Index.tsx, console-toolbar, tab bars), so left-placement needs coordinated layout changes in each header — the same class of work as the #164 AI-panel layout concern this issue references. Keeping this issue open for that remainder.