implemented window frame persistence for chat & settings windows

[RaajeevChandran]

Summary

This PR implements window frame persistence for both the chat and settings windows. The app now remembers the last closed size and position of these windows and restores them upon re-opening. fixes 622

Changes

• Behavior change
• UI change (screenshots below)
• Refactor / chore
• Tests
• Docs

Screen Recording

Screen.Recording.2026-03-15.at.7.50.42.AM.mov

Test Plan

1. Settings Window Persistence

• Action: Open Settings from the menu bar. Move it to a corner and resize the width significantly.
• Action: Close the Settings window.
• Action: Re-open Settings from the menu bar.
• Verification: The window should re-appear in the exact same corner with the custom width restored.

2. Chat Window Persistence

• Action: Open a Chat window. Move it and resize its width.
• Action: Close the window.
• Action: Re-open Chat.
• Verification: The first chat window should restore its previous position and width.

Checklist

• I have read CONTRIBUTING.md
• I added/updated tests where reasonable
• I updated docs/README as needed
• I verified build on macOS with Xcode 16.4+

[tpae]

This is amazing work. What happens when you start chat?

[RaajeevChandran]

Starting a chat won’t affect the window size