T-13: Preferences pane — When opening a project picker

[kirich1409]

Part of EPIC #193. Depends on #210.

Description

Add a "Projects" section to the Settings scene with a picker: "When opening a project: Ask each time / Always in same window / Always in new window". Bound to @AppStorage("projectOpenDisposition"). Choosing "Ask each time" resets any previously saved "Remember choice".

Acceptance Criteria

• Setting persists across launches
• Choosing "Ask each time" restores the prompt on the next menu-opened project
• Default value on fresh install = "Ask each time"
• Picker is accessibility-friendly (VoiceOver labels)

Module / Layer

Relay / Settings

Complexity

Small