What does this PR do?

• Fixes fix(editor): Add rounded corners and spacing to text selection dropdown in email body editor #25828
• Fixes CAL-6911

Visual Demo (For contributors especially)

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Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

Summary by cubic

Added spacing and rounded corners to the editor toolbar text selection dropdown to improve readability and consistency. Implements gap-1 on the toolbar and dropdown content and rounded-md on menu items and their buttons, aligning with CAL-6911.

^{Written for commit bd3c396. Summary will update automatically on new commits.}