Catppuccin Latte sets tab_bar_background #BCC0CC, a grey noticeably
darker than its #EFF1F5 background, so in light mode the tab bar sat on
a band of its own colour. kitty.conf leaves the setting commented out --
kitty's default is to follow the terminal background -- but the
generated *-theme.auto.conf files are applied with priority over
kitty.conf, so the theme won and there was nowhere left to override it.
repair-auto-themes.sh already normalises macos_titlebar_color for the
same reason; give tab_bar_background the same treatment. The canonical
copies under theme-modes stay exactly as the themes kitten saved them.
Also picks up the current theme choices: SpaceGray Eighties for dark,
Catppuccin Latte for light.
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