Inactive tabs have border, active tab has none

## Bug Description
Inactive tabs display a visible border/outline while the active tab has no border, creating a visual inconsistency in the tab bar.

## Steps to Reproduce
1. Install the Catppuccin theme extension in Brave on Linux Mint Cinnamon via [Chrome Web Store](https://chromewebstore.google.com/detail/catppuccin-chrome-theme-m/bkkmolkhemgaeaeggcmfbghljjjoofoh)
2. Opened multiple tabs
3. Observe that inactive tabs have a visible border while the active tab does not

## Expected Behaviour
Active tabs should have a border or a solid background while inactive tabs should have no background or border — the reverse of what currently happens..

## Environment
- OS: Linux Mint (Cinnamon desktop)
- Browser: Brave
- Theme: Catppuccin Chrome Theme - Mocha v-5.0.0

## Screenshots

Reproduce the tab-bar appearance in Brave on Linux Mint Cinnamon, then inspect the repository's theme source to locate the tab styling. Adjust the active and inactive states so the active tab has the visible border or solid background and the inactive tabs have neither, then verify the result with multiple tabs open.

Written by the indexing model from the issue text.