#426 fix(desktop): fix changes sidebar overflow and font sizing

Summary

• Replace ScrollArea with simple div + overflow-y-auto to fix horizontal overflow issues preventing text truncation
• Fix commit item font size to match file items (text-xs instead of text-sm)
• Fix commit item chevron size to match file items (w-3 h-3 instead of w-4 h-4)

Test plan

• Verify long commit messages truncate properly with ellipsis
• Verify stage/unstage all buttons are visible and right-aligned
• Verify commit items and file items have consistent font sizing

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