frontend: Adjust source context bar

[Warchamp7]

Description

Various tweaks and adjustments to the context bar appearance to bring it in line with the rest of the theme.

Motivation and Context

Want all aspects of the main window to look the same. Cleans up some UX quirks I was unhappy about.

The updated design follows @GeorgesStavracas' work on the obsproject/design repository. Some adjustments have been made after implementation and testing of the original design.

Original Mockup

Before

After

How Has This Been Tested?

👁

Types of changes

• Tweak (non-breaking change to improve existing functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.