The tab component in the viewer has a double border

[Angelmmiguel]

I found an issue related to the border of the session viewer component. The tabs and + button has a proper border (just 1px), while the rest of the row has a double border. It seems some border is overlapping or there's an incorrect 2px border.

We need to fix it so it has 1px border for the entire row.

[Angelmmiguel]

✅ Fixed — Issue #8: Double border in tab component

What was done:

• Identified and removed redundant border-b border-edge classes from the trailing fill div in TabBar.svelte
• The parent container was already providing the bottom border; the fill div's duplicate border was stacking on top

PR: #10 targeting main

The fix is minimal (one-line CSS removal) and ensures consistent 1px border across the entire tab row.