fix: tapping active mode segment incorrectly switches to opposite mode

[RaajeevChandran]

Summary

The Chat/Work mode toggle was firing a single toggle action on any tap, which always switched to the opposite mode regardless of which segment was tapped. Each segment now reports its own Mode back through the action closure and the caller guards against switching when the tapped mode is already active

Changes

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

Test Plan

1. Tap the Chat segment (already selected) - confirm nothing happens and the mode stays as Chat
2. Tap the Work segment - confirm the mode switches to Work
3. Tap the Work segment again (already selected) - confirm nothing happens and the mode stays as Work
4. Tap the Chat segment - confirm the mode switches back to Chat

Screenshots

Before

Before.mov

After

After.mov

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+