feat(app): visual improvements

[arvsrn]

Issue for this PR

N/A

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

• fixed terminal/review panel background
• fixed LineComment font in the review panel; was using mono
• terminal tabs now switch on mouse down instead of mouse up
• make UI text in the settings modal non-selectable
• added open state to the Add file button in the composer
• some minor alignment/spacing fixes

How did you verify your code works?

• Ran the app locally and verified the updated UI manually
• Ran type checks locally (bun turbo typecheck)

Screenshots / recordings

N/A

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

If you do not follow this template your PR will be automatically rejected.